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rfc:rfc2233

Network Working Group K. McCloghrie Request for Comments: 2233 Cisco Systems Obsoletes: 1573 F. Kastenholz Category: Standards Track FTP Software

                                                         November 1997
                The Interfaces Group MIB using SMIv2

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (1997).  All Rights Reserved.

Table of Contents

 1 Introduction ..............................................    2
 2 The SNMP Network Management Framework .....................    2
 2.1 Object Definitions ......................................    3
 3 Experience with the Interfaces Group ......................    3
 3.1 Clarifications/Revisions ................................    3
 3.1.1 Interface Sub-Layers ..................................    4
 3.1.2 Guidance on Defining Sub-layers .......................    6
 3.1.3 Virtual Circuits ......................................    8
 3.1.4 Bit, Character, and Fixed-Length Interfaces ...........    8
 3.1.5 Interface Numbering ...................................   10
 3.1.6 Counter Size ..........................................   14
 3.1.7 Interface Speed .......................................   16
 3.1.8 Multicast/Broadcast Counters ..........................   17
 3.1.9 Trap Enable ...........................................   18
 3.1.10 Addition of New ifType values ........................   18
 3.1.11 InterfaceIndex Textual Convention ....................   18
 3.1.12 New states for IfOperStatus ..........................   19
 3.1.13 IfAdminStatus and IfOperStatus .......................   20
 3.1.14 IfOperStatus in an Interface Stack ...................   21
 3.1.15 Traps ................................................   21
 3.1.16 ifSpecific ...........................................   23
 3.1.17 Creation/Deletion of Interfaces ......................   24
 3.1.18 All Values Must be Known .............................   24
 4 Media-Specific MIB Applicability ..........................   25

McCloghrie & Kastenholz Standards Track [Page 1] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 5 Overview ..................................................   26
 6 Interfaces Group Definitions ..............................   26
 7 Acknowledgements ..........................................   64
 8 References ................................................   64
 9 Security Considerations ...................................   65
 10 Authors' Addresses .......................................   65
 11 Full Copyright Statement .................................   66

1. Introduction

 This memo defines a portion of the Management Information Base
 (MIB) for use with network management protocols in the Internet
 community.  In particular, it describes managed objects used for
 managing Network Interfaces.
 This memo discusses the 'interfaces' group of MIB-II, especially the
 experience gained from the definition of numerous media- specific MIB
 modules for use in conjunction with the 'interfaces' group for
 managing various sub-layers beneath the internetwork- layer.  It
 specifies clarifications to, and extensions of, the architectural
 issues within the previous model used for the 'interfaces' group.
 This memo also includes a MIB module.  As well as including new
 MIB definitions to support the architectural extensions, this MIB
 module also re-specifies the 'interfaces' group of MIB-II in a
 manner that is both compliant to the SNMPv2 SMI and semantically-
 identical to the existing SNMPv1-based definitions.
 The key words "MUST" and "MUST NOT" in this document are to be
 interpreted as described in RFC 2119 [10].

2. The SNMP Network Management Framework

 The SNMP Network Management Framework presently consists of three
 major components.  They are:
 o    RFC 1902 which defines the SMI, the mechanisms used for
      describing and naming objects for the purpose of management.
 o    STD 17, RFC 1213 defines MIB-II, the core set of managed
      objects for the Internet suite of protocols.
 o    STD 15, RFC 1157 and RFC 1905 which define two versions of
      the protocol used for network access to managed objects.

McCloghrie & Kastenholz Standards Track [Page 2] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 The Framework permits new objects to be defined for the purpose of
 experimentation and evaluation.

2.1. Object Definitions

 Managed objects are accessed via a virtual information store,
 termed the Management Information Base or MIB.  Objects in the MIB
 are defined using the subset of Abstract Syntax Notation One
 (ASN.1) defined in the SMI.  In particular, each object object
 type is named by an OBJECT IDENTIFIER, an administratively
 assigned name.  The object type together with an object instance
 serves to uniquely identify a specific instantiation of the
 object.  For human convenience, we often use a textual string,
 termed the descriptor, to refer to the object type.

3. Experience with the Interfaces Group

 One of the strengths of internetwork-layer protocols such as IP
 [6] is that they are designed to run over any network interface.
 In achieving this, IP considers any and all protocols it runs over
 as a single "network interface" layer.  A similar view is taken by
 other internetwork-layer protocols.  This concept is represented
 in MIB-II by the 'interfaces' group which defines a generic set of
 managed objects such that any network interface can be managed in
 an interface-independent manner through these managed objects.
 The 'interfaces' group provides the means for additional managed
 objects specific to particular types of network interface (e.g., a
 specific medium such as Ethernet) to be defined as extensions to
 the 'interfaces' group for media-specific management.  Since the
 standardization of MIB-II, many such media-specific MIB modules
 have been defined.
 Experience in defining these media-specific MIB modules has shown
 that the model defined by MIB-II is too simplistic and/or static
 for some types of media-specific management.  As a result, some of
 these media-specific MIB modules assume an evolution or loosening
 of the model.  This memo documents and standardizes that evolution
 of the model and fills in the gaps caused by that evolution.  This
 memo also incorporates the interfaces group extensions documented
 in RFC 1229 [7].

3.1. Clarifications/Revisions

 There are several areas for which experience has indicated that
 clarification, revision, or extension of the model would be
 helpful.  The following sections discuss the changes in the
 interfaces group adopted by this memo in each of these areas.

McCloghrie & Kastenholz Standards Track [Page 3] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 In some sections, one or more paragraphs contain discussion of
 rejected alternatives to the model adopted in this memo.  Readers
 not familiar with the MIB-II model and not interested in the
 rationale behind the new model may want to skip these paragraphs.

3.1.1. Interface Sub-Layers

 Experience in defining media-specific management information has
 shown the need to distinguish between the multiple sub-layers
 beneath the internetwork-layer.  In addition, there is a need to
 manage these sub-layers in devices (e.g., MAC-layer bridges) which
 are unaware of which, if any, internetwork protocols run over
 these sub-layers.  As such, a model of having a single conceptual
 row in the interfaces table (MIB-II's ifTable) represent a whole
 interface underneath the internetwork-layer, and having a single
 associated media-specific MIB module (referenced via the ifType
 object) is too simplistic.  A further problem arises with the
 value of the ifType object which has enumerated values for each
 type of interface.
 Consider, for example, an interface with PPP running over an HDLC
 link which uses a RS232-like connector.  Each of these sub-layers
 has its own media-specific MIB module.  If all of this is
 represented by a single conceptual row in the ifTable, then an
 enumerated value for ifType is needed for that specific
 combination which maps to the specific combination of media-
 specific MIBs.  Furthermore, such a model still lacks a method to
 describe the relationship of all the sub-layers of the MIB stack.
 An associated problem is that of upward and downward multiplexing
 of the sub-layers.  An example of upward multiplexing is MLP
 (Multi-Link-Procedure) which provides load-sharing over several
 serial lines by appearing as a single point-to-point link to the
 sub-layer(s) above.  An example of downward multiplexing would be
 several instances of PPP, each framed within a separate X.25
 virtual circuit, all of which run over one fractional T1 channel,
 concurrently with other uses of the T1 link.  The MIB structure
 must allow these sorts of relationships to be described.
 Several solutions for representing multiple sub-layers were
 rejected.  One was to retain the concept of one conceptual row for
 all the sub-layers of an interface and have each media-specific
 MIB module identify its "superior" and "subordinate" sub-layers
 through OBJECT IDENTIFIER "pointers".  This scheme would have
 several drawbacks: the superior/subordinate pointers would be
 contained in the media-specific MIB modules; thus, a manager could
 not learn the structure of an interface without inspecting
 multiple pointers in different MIB modules; this would be overly

McCloghrie & Kastenholz Standards Track [Page 4] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 complex and only possible if the manager had knowledge of all the
 relevant media-specific MIB modules; MIB modules would all need to
 be retrofitted with these new "pointers"; this scheme would not
 adequately address the problem of upward and downward
 multiplexing; and finally, enumerated values of ifType would be
 needed for each combination of sub-layers.  Another rejected
 solution also retained the concept of one conceptual row for all
 the sub-layers of an interface but had a new separate MIB table to
 identify the "superior" and "subordinate" sub-layers and to
 contain OBJECT IDENTIFIER "pointers" to the media-specific MIB
 module for each sub-layer.  Effectively, one conceptual row in the
 ifTable would represent each combination of sub-layers between the
 internetwork-layer and the wire.  While this scheme has fewer
 drawbacks, it still would not support downward multiplexing, such
 as PPP over MLP: observe that MLP makes two (or more) serial
 lines appear to the layers above as a single physical interface,
 and thus PPP over MLP should appear to the internetwork-layer as a
 single interface; in contrast, this scheme would result in two (or
 more) conceptual rows in the ifTable, both of which the
 internetwork-layer would run over.  This scheme would also require
 enumerated values of ifType for each combination of sub-layers.
 The solution adopted by this memo is to have an individual
 conceptual row in the ifTable to represent each sub-layer, and
 have a new separate MIB table (the ifStackTable, see section 6
 below) to identify the "superior" and "subordinate" sub-layers
 through INTEGER "pointers" to the appropriate conceptual rows in
 the ifTable.  This solution supports both upward and downward
 multiplexing, allows the IANAifType to Media-Specific MIB mapping
 to identify the media-specific MIB module for that sub-layer, such
 that the new table need only be referenced to obtain information
 about layering, and it only requires enumerated values of ifType
 for each sub-layer, not for combinations of them.  However, it
 does require that the descriptions of some objects in the ifTable
 (specifically, ifType, ifPhysAddress, ifInUcastPkts, and
 ifOutUcastPkts) be generalized so as to apply to any sub-layer
 (rather than only to a sub-layer immediately beneath the network
 layer as previously), plus some (specifically, ifSpeed) which need
 to have appropriate values identified for use when a generalized
 definition does not apply to a particular sub-layer.
 In addition, this adopted solution makes no requirement that a
 device, in which a sub-layer is instrumented by a conceptual row
 of the ifTable, be aware of whether an internetwork protocol runs
 on top of (i.e., at some layer above) that sub-layer.  In fact,
 the counters of packets received on an interface are defined as
 counting the number "delivered to a higher-layer protocol".  This
 meaning of "higher-layer" includes:

McCloghrie & Kastenholz Standards Track [Page 5] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 (1)  Delivery to a forwarding module which accepts
      packets/frames/octets and forwards them on at the same
      protocol layer.  For example, for the purposes of this
      definition, the forwarding module of a MAC-layer bridge is
      considered as a "higher-layer" to the MAC-layer of each port
      on the bridge.
 (2)  Delivery to a higher sub-layer within a interface stack.  For
      example, for the purposes of this definition, if a PPP module
      operated directly over a serial interface, the PPP module
      would be considered the higher sub-layer to the serial
      interface.
 (3)  Delivery to a higher protocol layer which does not do packet
      forwarding for sub-layers that are "at the top of" the
      interface stack.  For example, for the purposes of this
      definition, the local IP module would be considered the
      higher layer to a SLIP serial interface.
 Similarly, for output, the counters of packets transmitted out an
 interface are defined as counting the number "that higher-level
 protocols requested to be transmitted".  This meaning of "higher-
 layer" includes:
 (1)  A forwarding module, at the same protocol layer, which
      transmits packets/frames/octets that were received on an
      different interface.  For example, for the purposes of this
      definition, the forwarding module of a MAC-layer bridge is
      considered as a "higher-layer" to the MAC-layer of each port
      on the bridge.
 (2)  The next higher sub-layer within an interface stack.  For
      example, for the purposes of this definition, if a PPP module
      operated directly over a serial interface, the PPP module
      would be a "higher layer" to the serial interface.
 (3)  For sub-layers that are "at the top of" the interface stack,
      a higher element in the network protocol stack.  For example,
      for the purposes of this definition, the local IP module
      would be considered the higher layer to an Ethernet
      interface.

3.1.2. Guidance on Defining Sub-layers

 The designer of a media-specific MIB must decide whether to divide
 the interface into sub-layers or not, and if so, how to make the
 divisions.  The following guidance is offered to assist the
 media-specific MIB designer in these decisions.

McCloghrie & Kastenholz Standards Track [Page 6] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 In general, the number of entries in the ifTable should be kept to
 the minimum required for network management.  In particular, a
 group of related interfaces should be treated as a single
 interface with one entry in the ifTable providing that:
 (1)  None of the group of interfaces performs multiplexing for any
      other interface in the agent,
 (2)  There is a meaningful and useful way for all of the ifTable's
      information (e.g., the counters, and the status variables),
      and all of the ifTable's capabilities (e.g., write access to
      ifAdminStatus), to apply to the group of interfaces as a
      whole.
 Under these circumstances, there should be one entry in the
 ifTable for such a group of interfaces, and any internal structure
 which needs to be represented to network management should be
 captured in a MIB module specific to the particular type of
 interface.
 Note that application of bullet 2 above to the ifTable's ifType
 object requires that there is a meaningful media-specific MIB and
 a meaningful ifType value which apply to the group of interfaces
 as a whole.  For example, it is not appropriate to treat an HDLC
 sub-layer and an RS-232 sub-layer as a single ifTable entry when
 the media-specific MIBs and the ifType values for HDLC and RS-232
 are separate (rather than combined).
 Subject to the above, it is appropriate to assign an ifIndex value
 to any interface that can occur in an interface stack (in the
 ifStackTable) where the bottom of the stack is a physical
 interface (ifConnectorPresent has the value 'true') and there is a
 layer-3 or other application that "points down" to the top of this
 stack.  An example of an application that points down to the top
 of the stack is the Character MIB [9].
 Note that the sub-layers of an interface on one device will
 sometimes be different from the sub-layers of the interconnected
 interface of another device; for example, for a frame-relay DTE
 interface connected a frameRelayService interface, the inter-
 connected DTE and DCE interfaces have different ifType values and
 media-specific MIBs.
 These guidelines are just that, guidelines.  The designer of a
 media-specific MIB is free to lay out the MIB in whatever SMI
 conformant manner is desired.  However, in doing so, the media-
 specific MIB MUST completely specify the sub-layering model used
 for the MIB, and provide the assumptions, reasoning, and rationale
 used to develop that model.

McCloghrie & Kastenholz Standards Track [Page 7] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

3.1.3. Virtual Circuits

 Several of the sub-layers for which media-specific MIB modules
 have been defined are connection oriented (e.g., Frame Relay,
 X.25).  Experience has shown that each effort to define such a MIB
 module revisits the question of whether separate conceptual rows
 in the ifTable are needed for each virtual circuit.  Most, if not
 all, of these efforts to date have decided to have all virtual
 circuits reference a single conceptual row in the ifTable.
 This memo strongly recommends that connection-oriented sub-layers
 do not have a conceptual row in the ifTable for each virtual
 circuit.  This avoids the proliferation of conceptual rows,
 especially those which have considerable redundant information.
 (Note, as a comparison, that connection-less sub-layers do not
 have conceptual rows for each remote address.)  There may,
 however, be circumstances under which it is appropriate for a
 virtual circuit of a connection-oriented sub-layer to have its own
 conceptual row in the ifTable; an example of this might be PPP
 over an X.25 virtual circuit.  The MIB in section 6 of this memo
 supports such circumstances.
 If a media-specific MIB wishes to assign an entry in the ifTable
 to each virtual circuit, the MIB designer must present the
 rationale for this decision in the media-specific MIB's
 specification.

3.1.4. Bit, Character, and Fixed-Length Interfaces

 RS-232 is an example of a character-oriented sub-layer over which
 (e.g., through use of PPP) IP datagrams can be sent.  Due to the
 packet-based nature of many of the objects in the ifTable,
 experience has shown that it is not appropriate to have a
 character-oriented sub-layer represented by a whole conceptual row
 in the ifTable.
 Experience has also shown that it is sometimes desirable to have
 some management information for bit-oriented interfaces, which are
 similarly difficult to represent by a whole conceptual row in the
 ifTable.  For example, to manage the channels of a DS1 circuit,
 where only some of the channels are carrying packet-based data.
 A further complication is that some subnetwork technologies
 transmit data in fixed length transmission units.  One example of
 such a technology is cell relay, and in particular Asynchronous
 Transfer Mode (ATM), which transmits data in fixed-length cells.
 Representing such a interface as a packet-based interface produces

McCloghrie & Kastenholz Standards Track [Page 8] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 redundant objects if the relationship between the number of
 packets and the number of octets in either direction is fixed by
 the size of the transmission unit (e.g., the size of a cell).
 About half the objects in the ifTable are applicable to every type
 of interface: packet-oriented, character-oriented, and bit-
 oriented.  Of the other half, two are applicable to both
 character-oriented and packet-oriented interfaces, and the rest
 are applicable only to packet-oriented interfaces.  Thus, while it
 is desirable for consistency to be able to represent any/all types
 of interfaces in the ifTable, it is not possible to implement the
 full ifTable for bit- and character-oriented sub-layers.
 A rejected solution to this problem would be to split the ifTable
 into two (or more) new MIB tables, one of which would contain
 objects that are relevant only to packet-oriented interfaces
 (e.g., PPP), and another that may be used by all interfaces.  This
 is highly undesirable since it would require changes in every
 agent implementing the ifTable (i.e., just about every existing
 SNMP agent).
 The solution adopted in this memo builds upon the fact that
 compliance statements in SNMPv2 (in contrast to SNMPv1) refer to
 object groups, where object groups are explicitly defined by
 listing the objects they contain.  Thus, in SNMPv2, multiple
 compliance statements can be specified, one for all interfaces and
 additional ones for specific types of interfaces.  The separate
 compliance statements can be based on separate object groups,
 where the object group for all interfaces can contain only those
 objects from the ifTable which are appropriate for every type of
 interfaces.  Using this solution, every sub-layer can have its own
 conceptual row in the ifTable.
 Thus, section 6 of this memo contains definitions of the objects
 of the existing 'interfaces' group of MIB-II, in a manner which is
 both SNMPv2-compliant and semantically-equivalent to the existing
 MIB-II definitions.  With equivalent semantics, and with the BER
 ("on the wire") encodings unchanged, these definitions retain the
 same OBJECT IDENTIFIER values as assigned by MIB-II.  Thus, in
 general, no rewrite of existing agents which conform to MIB-II and
 the ifExtensions MIB is required.
 In addition, this memo defines several object groups for the
 purposes of defining which objects apply to which types of
 interface:

McCloghrie & Kastenholz Standards Track [Page 9] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 (1)  the ifGeneralInformationGroup.  This group contains those
      objects applicable to all types of network interfaces,
      including bit-oriented interfaces.
 (2)  the ifPacketGroup.  This group contains those objects
      applicable to packet-oriented network interfaces.
 (3)  the ifFixedLengthGroup.  This group contains the objects
      applicable not only to character-oriented interfaces, such as
      RS-232, but also to those subnetwork technologies, such as
      cell-relay/ATM, which transmit data in fixed length
      transmission units.  As well as the octet counters, there are
      also a few other counters (e.g., the error counters) which
      are useful for this type of interface, but are currently
      defined as being packet-oriented.  To accommodate this, the
      definitions of these counters are generalized to apply to
      character-oriented interfaces and fixed-length-transmission
      interfaces.
 It should be noted that the octet counters in the ifTable
 aggregate octet counts for unicast and non-unicast packets into a
 single octet counter per direction (received/transmitted).  Thus,
 with the above definition of fixed-length-transmission interfaces,
 where such interfaces which support non-unicast packets, separate
 counts of unicast and multicast/broadcast transmissions can only
 be maintained in a media-specific MIB module.

3.1.5. Interface Numbering

 MIB-II defines an object, ifNumber, whose value represents:
      "The number of network interfaces (regardless of their
      current state) present on this system."
 Each interface is identified by a unique value of the ifIndex
 object, and the description of ifIndex constrains its value as
 follows:
      "Its value ranges between 1 and the value of ifNumber.  The
      value for each interface must remain constant at least from
      one re-initialization of the entity's network management
      system to the next re-initialization."
 This constancy requirement on the value of ifIndex for a
 particular interface is vital for efficient management.  However,
 an increasing number of devices allow for the dynamic
 addition/removal of network interfaces.  One example of this is a
 dynamic ability to configure the use of SLIP/PPP over a

McCloghrie & Kastenholz Standards Track [Page 10] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 character-oriented port.  For such dynamic additions/removals, the
 combination of the constancy requirement and the restriction that
 the value of ifIndex is less than ifNumber is problematic.
 Redefining ifNumber to be the largest value of ifIndex was
 rejected since it would not help.  Such a re-definition would
 require ifNumber to be deprecated and the utility of the redefined
 object would be questionable.  Alternatively, ifNumber could be
 deprecated and not replaced.  However, the deprecation of ifNumber
 would require a change to that portion of ifIndex's definition
 which refers to ifNumber.  So, since the definition of ifIndex
 must be changed anyway in order to solve the problem, changes to
 ifNumber do not benefit the solution.
 The solution adopted in this memo is just to delete the
 requirement that the value of ifIndex must be less than the value
 of ifNumber, and to retain ifNumber with its current definition.
 This is a minor change in the semantics of ifIndex; however, all
 existing agent implementations conform to this new definition, and
 in the interests of not requiring changes to existing agent
 implementations and to the many existing media-specific MIBs, this
 memo assumes that this change does not require ifIndex to be
 deprecated.  Experience indicates that this assumption does
 "break" a few management applications, but this is considered
 preferable to breaking all agent implementations.
 This solution also results in the possibility of "holes" in the
 ifTable, i.e., the ifIndex values of conceptual rows in the
 ifTable are not necessarily contiguous, but SNMP's GetNext (and
 SNMPv2's GetBulk) operation easily deals with such holes.  The
 value of ifNumber still represents the number of conceptual rows,
 which increases/decreases as new interfaces are dynamically
 added/removed.
 The requirement for constancy (between re-initializations) of an
 interface's ifIndex value is met by requiring that after an
 interface is dynamically removed, its ifIndex value is not re-used
 by a *different* dynamically added interface until after the
 following re-initialization of the network management system.
 This avoids the need for assignment (in advance) of ifIndex values
 for all possible interfaces that might be added dynamically.  The
 exact meaning of a "different" interface is hard to define, and
 there will be gray areas.  Any firm definition in this document
 would likely to turn out to be inadequate.  Instead, implementors
 must choose what it means in their particular situation, subject
 to the following rules:

McCloghrie & Kastenholz Standards Track [Page 11] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 (1)  a previously-unused value of ifIndex must be assigned to a
      dynamically added interface if an agent has no knowledge of
      whether the interface is the "same" or "different" to a
      previously incarnated interface.
 (2)  a management station, not noticing that an interface has gone
      away and another has come into existence, must not be
      confused when calculating the difference between the counter
      values retrieved on successive polls for a particular ifIndex
      value.
 When the new interface is the same as an old interface, but a
 discontinuity in the value of the interface's counters cannot be
 avoided, the ifTable has (until now) required that a new ifIndex
 value be assigned to the returning interface.  That is, either all
 counter values have had to be retained during the absence of an
 interface in order to use the same ifIndex value on that
 interface's return, or else a new ifIndex value has had to be
 assigned to the returning interface.  Both alternatives have
 proved to be burdensome to some implementations:
 (1)  maintaining the counter values may not be possible (e.g., if
      they are maintained on removable hardware),
 (2)  using a new ifIndex value presents extra work for management
      applications.  While the potential need for such extra work
      is unavoidable on agent re-initializations, it is desirable
      to avoid it between re-initializations.
 To address this, a new object, ifCounterDiscontinuityTime, has
 been defined to record the time of the last discontinuity in an
 interface's counters.  By monitoring the value of this new object,
 a management application can now detect counter discontinuities
 without the ifIndex value of the interface being changed.  Thus,
 an agent which implements this new object should, when a new
 interface is the same as an old interface, retain that interface's
 ifIndex value and update if necessary the interface's value of
 ifCounterDiscontinuityTime.  With this new object, a management
 application must, when calculating differences between counter
 values retrieved on successive polls, discard any calculated
 difference for which the value of ifCounterDiscontinuityTime is
 different for the two polls.  (Note that this test must be
 performed in addition to the normal checking of sysUpTime to
 detect an agent re-initialization.)  Since such discards are a
 waste of network management processing and bandwidth, an agent
 should not update the value of ifCounterDiscontinuityTime unless
 absolutely necessary.

McCloghrie & Kastenholz Standards Track [Page 12] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 While defining this new object is a change in the semantics of the
 ifTable counter objects, it is impractical to deprecate and
 redefine all these counters because of their wide deployment and
 importance.  Also, a survey of implementations indicates that many
 agents and management applications do not correctly implement this
 aspect of the current semantics (because of the burdensome issues
 mentioned above), such that the practical implications of such a
 change is small.  Thus, this breach of the SMI's rules is
 considered to be acceptable.
 Note, however, that the addition of ifCounterDiscontinuityTime
 does not change the fact that:
      It is necessary at certain times for the assignment of ifIndex
      values to change on a reinitialization of the agent (such as a
      reboot).
 The possibility of ifIndex value re-assignment must be
 accommodated by a management application whenever the value of
 sysUpTime is reset to zero.
 Note also that some agents support multiple "naming scopes", e.g.,
 for an SNMPv1 agent, multiple values of the SNMPv1 community
 string.  For such an agent (e.g., a CNM agent which supports a
 different subset of interfaces for different customers), there is
 no required relationship between the ifIndex values which identify
 interfaces in one naming scope and those which identify interfaces
 in another naming scope.  It is the agent's choice as to whether
 the same or different ifIndex values identify the same or
 different interfaces in different naming scopes.
 Because of the restriction of the value of ifIndex to be less than
 ifNumber, interfaces have been numbered with small integer values.
 This has led to the ability by humans to use the ifIndex values as
 (somewhat) user-friendly names for network interfaces (e.g.,
 "interface number 3").  With the relaxation of the restriction on
 the value of ifIndex, there is now the possibility that ifIndex
 values could be assigned as very large numbers (e.g., memory
 addresses).  Such numbers would be much less user-friendly.
 Therefore, this memo recommends that ifIndex values still be
 assigned as (relatively) small integer values starting at 1, even
 though the values in use at any one time are not necessarily
 contiguous.  (Note that this makes remembering which values have
 been assigned easy for agents which dynamically add new
 interfaces).

McCloghrie & Kastenholz Standards Track [Page 13] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 A new problem is introduced by representing each sub-layer as an
 ifTable entry.  Previously, there usually was a simple, direct,
 mapping of interfaces to the physical ports on systems.  This
 mapping would be based on the ifIndex value.  However, by having
 an ifTable entry for each interface sub-layer, mapping from
 interfaces to physical ports becomes increasingly problematic.
 To address this issue, a new object, ifName, is added to the MIB.
 This object contains the device's local name (e.g., the name used
 at the device's local console) for the interface of which the
 relevant entry in the ifTable is a component.  For example,
 consider a router having an interface composed of PPP running over
 an RS-232 port.  If the router uses the name "wan1" for the
 (combined) interface, then the ifName objects for the
 corresponding PPP and RS-232 entries in the ifTable would both
 have the value "wan1".  On the other hand, if the router uses the
 name "wan1.1" for the PPP interface and "wan1.2" for the RS-232
 port, then the ifName objects for the corresponding PPP and RS-232
 entries in the ifTable would have the values "wan1.1" and
 "wan1.2", respectively.  As an another example, consider an agent
 which responds to SNMP queries concerning an interface on some
 other (proxied) device: if such a proxied device associates a
 particular identifier with an interface, then it is appropriate to
 use this identifier as the value of the interface's ifName, since
 the local console in this case is that of the proxied device.
 In contrast, the existing ifDescr object is intended to contain a
 description of an interface, whereas another new object, ifAlias,
 provides a location in which a network management application can
 store a non-volatile interface-naming value of its own choice.
 The ifAlias object allows a network manager to give one or more
 interfaces their own unique names, irrespective of any interface-
 stack relationship.  Further, the ifAlias name is non-volatile,
 and thus an interface must retain its assigned ifAlias value
 across reboots, even if an agent chooses a new ifIndex value for
 the interface.

3.1.6. Counter Size

 As the speed of network media increase, the minimum time in which
 a 32 bit counter will wrap decreases.  For example, a 10Mbs stream
 of back-to-back, full-size packets causes ifInOctets to wrap in
 just over 57 minutes; at 100Mbs, the minimum wrap time is 5.7
 minutes, and at 1Gbs, the minimum is 34 seconds.  Requiring that
 interfaces be polled frequently enough not to miss a counter wrap
 is increasingly problematic.

McCloghrie & Kastenholz Standards Track [Page 14] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 A rejected solution to this problem was to scale the counters; for
 example, ifInOctets could be changed to count received octets in,
 say, 1024 byte blocks.  While it would provide acceptable
 functionality at high rates of the counted-events, at low rates it
 suffers.  If there is little traffic on an interface, there might
 be a significant interval before enough of the counted-events
 occur to cause the scaled counter to be incremented.  Traffic
 would then appear to be very bursty, leading to incorrect
 conclusions of the network's performance.
 Instead, this memo adopts expanded, 64 bit, counters.  These
 counters are provided in new "high capacity" groups.  The old,
 32-bit, counters have not been deprecated.  The 64-bit counters
 are to be used only when the 32-bit counters do not provide enough
 capacity; that is, when the 32 bit counters could wrap too fast.
 For interfaces that operate at 20,000,000 (20 million) bits per
 second or less, 32-bit byte and packet counters MUST be used.  For
 interfaces that operate faster than 20,000,000 bits/second, and
 slower than 650,000,000 bits/second, 32-bit packet counters MUST
 be used and 64-bit octet counters MUST be used.  For interfaces
 that operate at 650,000,000 bits/second or faster, 64-bit packet
 counters AND 64-bit octet counters MUST be used.
 These speed thresholds were chosen as reasonable compromises based
 on the following:
 (1)  The cost of maintaining 64-bit counters is relatively high,
      so minimizing the number of agents which must support them is
      desirable.  Common interfaces (such as 10Mbs Ethernet) should
      not require them.
 (2)  64-bit counters are a new feature, introduced in SNMPv2.  It
      is reasonable to expect that support for them will be spotty
      for the immediate future.  Thus, we wish to limit them to as
      few systems as possible.  This, in effect, means that 64-bit
      counters should be limited to higher speed interfaces.
      Ethernet (10,000,000 bps) and Token Ring (16,000,000 bps) are
      fairly wide-spread so it seems reasonable to not require 64-
      bit counters for these interfaces.
 (3)  The 32-bit octet counters will wrap in the following times,
      for the following interfaces (when transmitting maximum-sized
      packets back-to-back):
  1. 10Mbs Ethernet: 57 minutes,
  1. 16Mbs Token Ring: 36 minutes,

McCloghrie & Kastenholz Standards Track [Page 15] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

  1. a US T3 line (45 megabits): 12 minutes,
  1. FDDI: 5.7 minutes
 (4)  The 32-bit packet counters wrap in about 57 minutes when 64-
      byte packets are transmitted back-to-back on a 650,000,000
      bit/second link.
 As an aside, a 1-terabit/second (1,000 Gbs) link will cause a 64 bit
 octet counter to wrap in just under 5 years.  Conversely, an
 81,000,000 terabit/second link is required to cause a 64-bit counter
 to wrap in 30 minutes.  We believe that, while technology rapidly
 marches forward, this link speed will not be achieved for at least
 several years, leaving sufficient time to evaluate the introduction
 of 96 bit counters.
 When 64-bit counters are in use, the 32-bit counters MUST still be
 available.  They will report the low 32-bits of the associated 64-bit
 count (e.g., ifInOctets will report the least significant 32 bits of
 ifHCInOctets).  This enhances inter-operability with existing
 implementations at a very minimal cost to agents.
 The new "high capacity" groups are:
 (1)  the ifHCFixedLengthGroup for character-oriented/fixed-length
      interfaces, and the ifHCPacketGroup for packet-based interfaces;
      both of these groups include 64 bit counters for octets, and
 (2)  the ifVHCPacketGroup for packet-based interfaces; this group
      includes 64 bit counters for octets and packets.

3.1.7. Interface Speed

 Network speeds are increasing.  The range of ifSpeed is limited to
 reporting a maximum speed of (2**31)-1 bits/second, or approximately
 2.2Gbs.  SONET defines an OC-48 interface, which is defined at
 operating at 48 times 51 Mbs, which is a speed in excess of 2.4Gbs.
 Thus, ifSpeed is insufficient for the future, and this memo defines
 an additional object: ifHighSpeed.
 The ifHighSpeed object reports the speed of the interface in
 1,000,000 (1 million) bits/second units.  Thus, the true speed of the
 interface will be the value reported by this object, plus or minus
 500,000 bits/second.

McCloghrie & Kastenholz Standards Track [Page 16] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 Other alternatives considered (but rejected) were:
 (1)  Making the interface speed a 64-bit gauge.  This was rejected
      since the current SMI does not allow such a syntax.
      Furthermore, even if 64-bit gauges were available, their use
      would require additional complexity in agents due to an
      increased requirement for 64-bit operations.
 (2)  We also considered making "high-32 bit" and "low-32-bit"
      objects which, when combined, would be a 64-bit value.  This
      simply seemed overly complex for what we are trying to do.
      Furthermore, a full 64-bits of precision does not seem
      necessary.  The value of ifHighSpeed will be the only report of
      interface speed for interfaces that are faster than
      4,294,967,295 bits per second.  At this speed, the granularity
      of ifHighSpeed will be 1,000,000 bits per second, thus the error
      will be 1/4294, or about 0.02%.  This seems reasonable.
 (3)  Adding a "scale" object, which would define the units which
      ifSpeed's value is.
      This would require two additional objects; one for the scaling
      object, and one to replace the current ifSpeed.  This later
      object is required since the semantics of ifSpeed would be
      significantly altered, and manager stations which do not
      understand the new semantics would be confused.

3.1.8. Multicast/Broadcast Counters

 In MIB-II, the ifTable counters for multicast and broadcast packets
 are combined as counters of non-unicast packets.  In contrast, the
 ifExtensions MIB [7] defined one set of counters for multicast, and a
 separate set for broadcast packets.  With the separate counters, the
 original combined counters become redundant.  To avoid this
 redundancy, the non-unicast counters are deprecated.
 For the output broadcast and multicast counters defined in RFC 1229,
 their definitions varied slightly from the packet counters in the
 ifTable, in that they did not count errors/discarded packets.  Thus,
 this memo defines new objects with better aligned definitions.
 Counters with 64 bits of range are also needed, as explained above.

McCloghrie & Kastenholz Standards Track [Page 17] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

3.1.9. Trap Enable

 In the multi-layer interface model, each sub-layer for which there is
 an entry in the ifTable can generate linkUp/Down Traps.  Since
 interface state changes would tend to propagate through the interface
 (from top to bottom, or bottom to top), it is likely that several
 traps would be generated for each linkUp/Down occurrence.
 It is desirable to provide a mechanism for manager stations to
 control the generation of these traps.  To this end, the
 ifLinkUpDownTrapEnable object has been added.  This object allows
 managers to limit generation of traps to just the sub-layers of
 interest.
 The default setting should limit the number of traps generated to one
 per interface per linkUp/Down event.  Furthermore, it seems that the
 state changes of most interest to network managers occur at the
 lowest level of an interface stack.  Therefore we specify that by
 default, only the lowest sub-layer of the interface generate traps.

3.1.10. Addition of New ifType values

 Over time, there is the need to add new ifType enumerated values for
 new interface types.  If the syntax of ifType were defined in the MIB
 in section 6, then a new version of this MIB would have to be re-
 issued in order to define new values.  In the past, re- issuing of a
 MIB has occurred only after several years.
 Therefore, the syntax of ifType is changed to be a textual
 convention, such that the enumerated integer values are now defined
 in the textual convention, IANAifType, defined in a different
 document.  This allows additional values to be documented without
 having to re-issue a new version of this document.  The Internet
 Assigned Number Authority (IANA) is responsible for the assignment of
 all Internet numbers, including various SNMP-related numbers, and
 specifically, new ifType values.

3.1.11. InterfaceIndex Textual Convention

 A new textual convention, InterfaceIndex, has been defined.  This
 textual convention "contains" all of the semantics of the ifIndex
 object.  This allows other mib modules to easily import the semantics
 of ifIndex.

McCloghrie & Kastenholz Standards Track [Page 18] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

3.1.12. New states for IfOperStatus

 Three new states have been added to ifOperStatus: 'dormant', 
 'notPresent', and 'lowerLayerDown'.
 The dormant state indicates that the relevant interface is not
 actually in a condition to pass packets (i.e., it is not "up") but is
 in a "pending" state, waiting for some external event.  For "on-
 demand" interfaces, this new state identifies the situation where the
 interface is waiting for events to place it in the up state.
 Examples of such events might be:
 (1)  having packets to transmit before establishing a connection
      to a remote system;
 (2)  having a remote system establish a connection to the
      interface (e.g. dialing up to a slip-server).
 The notPresent state is a refinement on the down state which
 indicates that the relevant interface is down specifically because
 some component (typically, a hardware component) is not present in
 the managed system.  Examples of use of the notPresent state are:
 (1)  to allow an interface's conceptual row including its counter
      values to be retained across a "hot swap" of a card/module,
      and/or
 (2)  to allow an interface's conceptual row to be created, and
      thereby enable interfaces to be pre-configured prior to
      installation of the hardware needed to make the interface
      operational.
 Agents are not required to support interfaces in the notPresent
 state.  However, from a conceptual viewpoint, when a row in the
 ifTable is created, it first enters the notPresent state and then
 subsequently transitions into the down state; similarly, when a row
 in the ifTable is deleted, it first enters the notPresent state and
 then subsequently the object instances are deleted.  For an agent
 with no support for notPresent, both of these transitions (from the
 notPresent state to the down state, and from the notPresent state to
 the instances being removed) are immediate, i.e., the transition does
 not last long enough to be recorded by ifOperStatus.  Even for those
 agents which do support interfaces in the notPresent state, the
 length of time and conditions under which an interface stays in the
 notPresent state is implementation-specific.

McCloghrie & Kastenholz Standards Track [Page 19] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 The lowerLayerDown state is also a refinement on the down state.
 This new state indicates that this interface runs "on top of" one or
 more other interfaces (see ifStackTable) and that this interface is
 down specifically because one or more of these lower-layer interfaces
 are down.

3.1.13. IfAdminStatus and IfOperStatus

 The down state of ifOperStatus now has two meanings, depending on the
 value of ifAdminStatus.
 (1)  if ifAdminStatus is not down and ifOperStatus is down then a
      fault condition is presumed to exist on the interface.
 (2)  if ifAdminStatus is down, then ifOperStatus will normally
      also be down (or notPresent) i.e., there is not (necessarily) a
      fault condition on the interface.
 Note that when ifAdminStatus transitions to down, ifOperStatus will
 normally also transition to down.  In this situation, it is possible
 that ifOperStatus's transition will not occur immediately, but rather
 after a small time lag to complete certain operations before going
 "down"; for example, it might need to finish transmitting a packet.
 If a manager station finds that ifAdminStatus is down and
 ifOperStatus is not down for a particular interface, the manager
 station should wait a short while and check again.  If the condition
 still exists, only then should it raise an error indication.
 Naturally, it should also ensure that ifLastChange has not changed
 during this interval.
 Whenever an interface table entry is created (usually as a result of
 system initialization), the relevant instance of ifAdminStatus is set
 to down, and presumably ifOperStatus will be down or notPresent.
 An interface may be enabled in two ways: either as a result of
 explicit management action (e.g. setting ifAdminStatus to up) or as a
 result of the managed system's initialization process.  When
 ifAdminStatus changes to the up state, the related ifOperStatus
 should do one of the following:
 (1)  Change to the up state if and only if the interface is able
      to send and receive packets.
 (2)  Change to the lowerLayerDown state if and only if the
      interface is prevented from entering the up state because of the
      state of one or more of the interfaces beneath it in the
      interface stack.

McCloghrie & Kastenholz Standards Track [Page 20] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 (3)  Change to the dormant state if and only if the interface is
      found to be operable, but the interface is waiting for other,
      external, events to occur before it can transmit or receive
      packets.  Presumably when the expected events occur, the
      interface will then change to the up state.
 (4)  Remain in the down state if an error or other fault condition
      is detected on the interface.
 (5)  Change to the unknown state if, for some reason, the state of
      the interface can not be ascertained.
 (6)  Change to the testing state if some test(s) must be performed
      on the interface. Presumably after completion of the test, the
      interface's state will change to up, dormant, or down, as
      appropriate.
 (7)  Remain in the notPresent state if interface components are
      missing.

3.1.14. IfOperStatus in an Interface Stack

 When an interface is a part of an interface-stack, but is not the
 lowest interface in the stack, then:
 (1)  ifOperStatus has the value 'up' if it is able to pass packets
      due to one or more interfaces below it in the stack being 'up',
      irrespective of whether other interfaces below it are 'down', 
      'dormant', 'notPresent', 'lowerLayerDown', 'unknown' or
      'testing'.
 (2)  ifOperStatus may have the value 'up' or 'dormant' if one or
      more interfaces below it in the stack are 'dormant', and all
      others below it are either 'down', 'dormant', 'notPresent',
      'lowerLayerDown', 'unknown' or 'testing'.
 (3)  ifOperStatus has the value 'lowerLayerDown' while all
      interfaces below it in the stack are either 'down',
      'notPresent', 'lowerLayerDown', or 'testing'.

3.1.15. Traps

 The exact definition of when linkUp and linkDown traps are generated
 has been changed to reflect the changes to ifAdminStatus and
 ifOperStatus.

McCloghrie & Kastenholz Standards Track [Page 21] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 Operational experience indicates that management stations are most
 concerned with an interface being in the down state and the fact that
 this state may indicate a failure.  Thus, it is most useful to
 instrument transitions into/out of either the up state or the down
 state.
 Instrumenting transitions into or out of the up state was rejected
 since it would have the drawback that a demand interface might have
 many transitions between up and dormant, leading to many linkUp traps
 and no linkDown traps.  Furthermore, if a node's only interface is
 the demand interface, then a transition to dormant would entail
 generation of a linkDown trap, necessitating bringing the link to the
 up state (and a linkUp trap)!!
 On the other hand, instrumenting transitions into or out of the down
 state (to/from all other states except notPresent) has the
 advantages:
 (1)  A transition into the down state (from a state other than
      notPresent) will occur when an error is detected on an
      interface.  Error conditions are presumably of great interest to
      network managers.
 (2)  Departing the down state (to a state other than the
      notPresent state) generally indicates that the interface is
      going to either up or dormant, both of which are considered
      "healthy" states.
 Furthermore, it is believed that generating traps on transitions into
 or out of the down state (except to/from the notPresent state) is
 generally consistent with current usage and interpretation of these
 traps by manager stations.
 Transitions to/from the notPresent state are concerned with the
 insertion and removal of hardware, and are outside the scope of these
 traps.
 Therefore, this memo defines that LinkUp and linkDown traps are
 generated on just after ifOperStatus leaves, or just before it
 enters, the down state, respectively; except that LinkUp and linkDown
 traps never generated on transitions to/from the notPresent state.
 Note that this definition allows a node with only one interface to
 transmit a linkDown trap before that interface goes down.  (Of
 course, when the interface is going down because of a failure
 condition, the linkDown trap probably cannot be successfully
 transmitted anyway.)

McCloghrie & Kastenholz Standards Track [Page 22] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 Some interfaces perform a link "training" function when trying to
 bring the interface up.  In the event that such an interface were
 defective, then the training function would fail and the interface
 would remain down, and the training function might be repeated at
 appropriate intervals.  If the interface, while performing this
 training function, were considered to the in the testing state, then
 linkUp and linkDown traps would be generated for each start and end
 of the training function.  This is not the intent of the linkUp and
 linkDown traps, and therefore, while performing such a training
 function, the interface's state should be represented as down.
 An exception to the above generation of linkUp/linkDown traps on
 changes in ifOperStatus, occurs when an interface is "flapping",
 i.e., when it is rapidly oscillating between the up and down states.
 If traps were generated for each such oscillation, the network and
 the network management system would be flooded with unnecessary
 traps.  In such a situation, the agent should rate- limit its
 generation of traps.

3.1.16. ifSpecific

 The original definition of the OBJECT IDENTIFIER value of ifSpecific
 was not sufficiently clear.  As a result, different implementors used
 it differently, and confusion resulted.  Some implementations set the
 value of ifSpecific to the OBJECT IDENTIFIER that defines the media-
 specific MIB, i.e., the "foo" of:
            foo OBJECT IDENTIFIER ::= { transmission xxx }
 while others set it to be OBJECT IDENTIFIER of the specific table or
 entry in the appropriate media-specific MIB (i.e., fooTable or
 fooEntry), while still others set it be the OBJECT IDENTIFIER of the
 index object of the table's row, including instance identifier,
 (i.e., fooIfIndex.ifIndex).  A definition based on the latter would
 not be sufficient unless it also allowed for media- specific MIBs
 which include several tables, where each table has its own
 (different) indexing.
 The only definition that can both be made explicit and can cover all
 the useful situations is to have ifSpecific be the most general value
 for the media-specific MIB module (the first example given above).
 This effectively makes it redundant because it contains no more
 information than is provided by ifType.  Thus, ifSpecific has been
 deprecated.

McCloghrie & Kastenholz Standards Track [Page 23] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

3.1.17. Creation/Deletion of Interfaces

 While some interfaces, for example, most physical interfaces, cannot
 be created via network management, other interfaces such as logical
 interfaces sometimes can be.  The ifTable contains only generic
 information about an interface.  Almost all 'create-able' interfaces
 have other, media-specific, information through which configuration
 parameters may be supplied prior to creating such an interface.
 Thus, the ifTable does not itself support the creation or deletion of
 an interface (specifically, it has no RowStatus [2] column).  Rather,
 if a particular interface type supports the dynamic creation and/or
 deletion of an interface of that type, then that media-specific MIB
 should include an appropriate RowStatus object (see the ATM LAN-
 Emulation Client MIB [8] for an example of a MIB which does this).
 Typically, when such a RowStatus object is created/deleted, then the
 conceptual row in the ifTable appears/disappears as a by-product, and
 an ifIndex value (chosen by the agent) is stored in an appropriate
 object in the media-specific MIB.

3.1.18. All Values Must be Known

 There are a number of situations where an agent does not know the
 value of one or more objects for a particular interface.  In all such
 circumstances, an agent MUST NOT instantiate an object with an
 incorrect value; rather, it MUST respond with the appropriate
 error/exception condition (e.g., noSuchInstance for SNMPv2).
 One example is where an agent is unable to count the occurrences
 defined by one (or more) of the ifTable counters.  In this
 circumstance, the agent MUST NOT instantiate the particular counter
 with a value of, say, zero.  To do so would be to provide mis-
 information to a network management application reading the zero
 value, and thereby assuming that there have been no occurrences of
 the event (e.g., no input errors because ifInErrors is always zero).
 Sometimes the lack of knowledge of an object's value is temporary.
 For example, when the MTU of an interface is a configured value and a
 device dynamically learns the configured value through (after)
 exchanging messages over the interface (e.g., ATM LAN- Emulation
 [8]).  In such a case, the value is not known until after the ifTable
 entry has already been created.  In such a case, the ifTable entry
 should be created without an instance of the object whose value is
 unknown; later, when the value becomes known, the missing object can
 then be instantiated (e.g., the instance of ifMtu is only
 instantiated once the interface's MTU becomes known).

McCloghrie & Kastenholz Standards Track [Page 24] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 As a result of this "known values" rule, management applications MUST
 be able to cope with the responses to retrieving the object instances
 within a conceptual row of the ifTable revealing that some of the
 row's columnar objects are missing/not available.

4. Media-Specific MIB Applicability

 The exact use and semantics of many objects in this MIB are open to
 some interpretation.  This is a result of the generic nature of this
 MIB.  It is not always possible to come up with specific,
 unambiguous, text that covers all cases and yet preserves the generic
 nature of the MIB.
 Therefore, it is incumbent upon a media-specific MIB designer to,
 wherever necessary, clarify the use of the objects in this MIB with
 respect to the media-specific MIB.
 Specific areas of clarification include
 Layering Model
      The media-specific MIB designer MUST completely and
      unambiguously specify the layering model used.  Each individual
      sub-layer must be identified, as must the ifStackTable's
      portrayal of the relationship(s) between the sub-layers.
 Virtual Circuits
      The media-specific MIB designer MUST specify whether virtual
      circuits are assigned entries in the ifTable or not.  If they
      are, compelling rationale must be presented.
 ifRcvAddressTable
      The media-specific MIB designer MUST specify the applicability
      of the ifRcvAddressTable.
 ifType
      For each of the ifType values to which the media-specific MIB
      applies, it must specify the mapping of ifType values to media-
      specific MIB module(s) and instances of MIB objects within those
      modules.
 However, wherever this interface MIB is specific in the semantics,
 DESCRIPTION, or applicability of objects, the media-specific MIB
 designer MUST NOT change said semantics, DESCRIPTION, or
 applicability.

McCloghrie & Kastenholz Standards Track [Page 25] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

5. Overview

 This MIB consists of 4 tables:
 ifTable
      This table is the ifTable from MIB-II.
      ifXTable
      This table contains objects that have been added to the
      Interface MIB as a result of the Interface Evolution effort, or
      replacements for objects of the original (MIB-II) ifTable that
      were deprecated because the semantics of said objects have
      significantly changed.  This table also contains objects that
      were previously in the ifExtnsTable.
 ifStackTable
      This table contains objects that define the relationships among
      the sub-layers of an interface.
 ifRcvAddressTable
      This table contains objects that are used to define the media-
      level addresses which this interface will receive.  This table
      is a generic table.  The designers of media- specific MIBs must
      define exactly how this table applies to their specific MIB.

6. Interfaces Group Definitions

 IF-MIB DEFINITIONS ::= BEGIN
 IMPORTS
     MODULE-IDENTITY, OBJECT-TYPE, Counter32, Gauge32, Counter64,
     Integer32, TimeTicks, mib-2,
     NOTIFICATION-TYPE                        FROM SNMPv2-SMI
     TEXTUAL-CONVENTION, DisplayString,
     PhysAddress, TruthValue, RowStatus,
     TimeStamp, AutonomousType, TestAndIncr   FROM SNMPv2-TC
     MODULE-COMPLIANCE, OBJECT-GROUP          FROM SNMPv2-CONF
     snmpTraps                                FROM SNMPv2-MIB
     IANAifType                               FROM IANAifType-MIB;

McCloghrie & Kastenholz Standards Track [Page 26] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 ifMIB MODULE-IDENTITY
     LAST-UPDATED "9611031355Z"
     ORGANIZATION "IETF Interfaces MIB Working Group"
     CONTACT-INFO
             "   Keith McCloghrie
                 Cisco Systems, Inc.
                 170 West Tasman Drive
                 San Jose, CA  95134-1706
                 US
                 408-526-5260
                 kzm@cisco.com"
     DESCRIPTION
             "The MIB module to describe generic objects for
             network interface sub-layers.  This MIB is an updated
             version of MIB-II's ifTable, and incorporates the
             extensions defined in RFC 1229."
     REVISION      "9602282155Z"
     DESCRIPTION
             "Revisions made by the Interfaces MIB WG."
     REVISION      "9311082155Z"
     DESCRIPTION
             "Initial revision, published as part of RFC 1573."
     ::= { mib-2 31 }
 ifMIBObjects OBJECT IDENTIFIER ::= { ifMIB 1 }
 interfaces   OBJECT IDENTIFIER ::= { mib-2 2 }
 OwnerString ::= TEXTUAL-CONVENTION
     DISPLAY-HINT "255a"
     STATUS       current
     DESCRIPTION
             "This data type is used to model an administratively
             assigned name of the owner of a resource.  This
             information is taken from the NVT ASCII character set.
             It is suggested that this name contain one or more of
             the following: ASCII form of the manager station's
             transport address, management station name (e.g.,
             domain name), network management personnel's name,
             location, or phone number.  In some cases the agent
             itself will be the owner of an entry.  In these cases,
             this string shall be set to a string starting with
             'agent'."
     SYNTAX       OCTET STRING (SIZE(0..255))

McCloghrie & Kastenholz Standards Track [Page 27] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

  1. - InterfaceIndex contains the semantics of ifIndex and
  2. - should be used for any objects defined on other mib
  3. - modules that need these semantics.
 InterfaceIndex ::= TEXTUAL-CONVENTION
     DISPLAY-HINT "d"
     STATUS       current
     DESCRIPTION
             "A unique value, greater than zero, for each interface
             or interface sub-layer in the managed system.  It is
             recommended that values are assigned contiguously
             starting from 1.  The value for each interface sub-
             layer must remain constant at least from one re-
             initialization of the entity's network management
             system to the next re-initialization."
     SYNTAX       Integer32 (1..2147483647)
 InterfaceIndexOrZero ::= TEXTUAL-CONVENTION
     DISPLAY-HINT "d"
     STATUS       current
     DESCRIPTION
             "This textual convention is an extension of the
             InterfaceIndex convention.  The latter defines a
             greater than zero value used to identify an interface
             or interface sub-layer in the managed system.  This
             extension permits the additional value of zero.  the
             value zero is object-specific and must therefore be
             defined as part of the description of any object which
             uses this syntax.  Examples of the usage of zero might
             include situations where interface was unknown, or
             when none or all interfaces need to be referenced."
     SYNTAX       Integer32 (0..2147483647)
 ifNumber  OBJECT-TYPE
     SYNTAX      Integer32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The number of network interfaces (regardless of their
             current state) present on this system."
     ::= { interfaces 1 }

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 ifTableLastChange  OBJECT-TYPE
     SYNTAX      TimeTicks
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The value of sysUpTime at the time of the last
             creation or deletion of an entry in the ifTable.  If
             the number of entries has been unchanged since the
             last re-initialization of the local network management
             subsystem, then this object contains a zero value."
     ::= { ifMIBObjects 5 }
  1. - the Interfaces table
  1. - The Interfaces table contains information on the entity's
  2. - interfaces. Each sub-layer below the internetwork-layer
  3. - of a network interface is considered to be an interface.
 ifTable OBJECT-TYPE
     SYNTAX      SEQUENCE OF IfEntry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
             "A list of interface entries.  The number of entries
             is given by the value of ifNumber."
     ::= { interfaces 2 }
 ifEntry OBJECT-TYPE
     SYNTAX      IfEntry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
             "An entry containing management information applicable
             to a particular interface."
     INDEX   { ifIndex }
     ::= { ifTable 1 }
 IfEntry ::=
     SEQUENCE {
         ifIndex                 InterfaceIndex,
         ifDescr                 DisplayString,
         ifType                  IANAifType,
         ifMtu                   Integer32,
         ifSpeed                 Gauge32,

McCloghrie & Kastenholz Standards Track [Page 29] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

         ifPhysAddress           PhysAddress,
         ifAdminStatus           INTEGER,
         ifOperStatus            INTEGER,
         ifLastChange            TimeTicks,
         ifInOctets              Counter32,
         ifInUcastPkts           Counter32,
         ifInNUcastPkts          Counter32,  -- deprecated
         ifInDiscards            Counter32,
         ifInErrors              Counter32,
         ifInUnknownProtos       Counter32,
         ifOutOctets             Counter32,
         ifOutUcastPkts          Counter32,
         ifOutNUcastPkts         Counter32,  -- deprecated
         ifOutDiscards           Counter32,
         ifOutErrors             Counter32,
         ifOutQLen               Gauge32,    -- deprecated
         ifSpecific              OBJECT IDENTIFIER -- deprecated
     }
 ifIndex OBJECT-TYPE
     SYNTAX      InterfaceIndex
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "A unique value, greater than zero, for each
             interface.  It is recommended that values are assigned
             contiguously starting from 1.  The value for each
             interface sub-layer must remain constant at least from
             one re-initialization of the entity's network
             management system to the next re-initialization."
     ::= { ifEntry 1 }
 ifDescr OBJECT-TYPE
     SYNTAX      DisplayString (SIZE (0..255))
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "A textual string containing information about the
             interface.  This string should include the name of the
             manufacturer, the product name and the version of the
             interface hardware/software."
     ::= { ifEntry 2 }

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 ifType OBJECT-TYPE
     SYNTAX      IANAifType
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The type of interface.  Additional values for ifType
             are assigned by the Internet Assigned Numbers
             Authority (IANA), through updating the syntax of the
             IANAifType textual convention."
     ::= { ifEntry 3 }
 ifMtu OBJECT-TYPE
     SYNTAX      Integer32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The size of the largest packet which can be
             sent/received on the interface, specified in octets.
             For interfaces that are used for transmitting network
             datagrams, this is the size of the largest network
             datagram that can be sent on the interface."
     ::= { ifEntry 4 }
 ifSpeed OBJECT-TYPE
     SYNTAX      Gauge32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "An estimate of the interface's current bandwidth in
             bits per second.  For interfaces which do not vary in
             bandwidth or for those where no accurate estimation
             can be made, this object should contain the nominal
             bandwidth.  If the bandwidth of the interface is
             greater than the maximum value reportable by this
             object then this object should report its maximum
             value (4,294,967,295) and ifHighSpeed must be used to
             report the interace's speed.  For a sub-layer which
             has no concept of bandwidth, this object should be
             zero."
     ::= { ifEntry 5 }
 ifPhysAddress OBJECT-TYPE
     SYNTAX      PhysAddress
     MAX-ACCESS  read-only
     STATUS      current

McCloghrie & Kastenholz Standards Track [Page 31] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

     DESCRIPTION
             "The interface's address at its protocol sub-layer.
             For example, for an 802.x interface, this object
             normally contains a MAC address.  The interface's
             media-specific MIB must define the bit and byte
             ordering and the format of the value of this object.
             For interfaces which do not have such an address
             (e.g., a serial line), this object should contain an
             octet string of zero length."
     ::= { ifEntry 6 }
 ifAdminStatus OBJECT-TYPE
     SYNTAX  INTEGER {
                 up(1),       -- ready to pass packets
                 down(2),
                 testing(3)   -- in some test mode
             }
     MAX-ACCESS  read-write
     STATUS      current
     DESCRIPTION
             "The desired state of the interface.  The testing(3)
             state indicates that no operational packets can be
             passed.  When a managed system initializes, all
             interfaces start with ifAdminStatus in the down(2)
             state.  As a result of either explicit management
             action or per configuration information retained by
             the managed system, ifAdminStatus is then changed to
             either the up(1) or testing(3) states (or remains in
             the down(2) state)."
     ::= { ifEntry 7 }
 ifOperStatus OBJECT-TYPE
     SYNTAX  INTEGER {
                 up(1),        -- ready to pass packets
                 down(2),
                 testing(3),   -- in some test mode
                 unknown(4),   -- status can not be determined
                               -- for some reason.
                 dormant(5),
                 notPresent(6),    -- some component is missing
                 lowerLayerDown(7) -- down due to state of
                                   -- lower-layer interface(s)
             }

McCloghrie & Kastenholz Standards Track [Page 32] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The current operational state of the interface.  The
             testing(3) state indicates that no operational packets
             can be passed.  If ifAdminStatus is down(2) then
             ifOperStatus should be down(2).  If ifAdminStatus is
             changed to up(1) then ifOperStatus should change to
             up(1) if the interface is ready to transmit and
             receive network traffic; it should change to
             dormant(5) if the interface is waiting for external
             actions (such as a serial line waiting for an incoming
             connection); it should remain in the down(2) state if
             and only if there is a fault that prevents it from
             going to the up(1) state; it should remain in the
             notPresent(6) state if the interface has missing
             (typically, hardware) components."
     ::= { ifEntry 8 }
 ifLastChange OBJECT-TYPE
     SYNTAX      TimeTicks
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The value of sysUpTime at the time the interface
             entered its current operational state.  If the current
             state was entered prior to the last re-initialization
             of the local network management subsystem, then this
             object contains a zero value."
     ::= { ifEntry 9 }
 ifInOctets OBJECT-TYPE
     SYNTAX      Counter32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The total number of octets received on the interface,
             including framing characters.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."
     ::= { ifEntry 10 }

McCloghrie & Kastenholz Standards Track [Page 33] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 ifInUcastPkts OBJECT-TYPE
     SYNTAX      Counter32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The number of packets, delivered by this sub-layer to
             a higher (sub-)layer, which were not addressed to a
             multicast or broadcast address at this sub-layer.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."
     ::= { ifEntry 11 }
 ifInNUcastPkts OBJECT-TYPE
     SYNTAX  Counter32
     MAX-ACCESS  read-only
     STATUS      deprecated
     DESCRIPTION
             "The number of packets, delivered by this sub-layer to
             a higher (sub-)layer, which were addressed to a
             multicast or broadcast address at this sub-layer.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime.
             This object is deprecated in favour of
             ifInMulticastPkts and ifInBroadcastPkts."
     ::= { ifEntry 12 }
 ifInDiscards OBJECT-TYPE
     SYNTAX      Counter32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The number of inbound packets which were chosen to be
             discarded even though no errors had been detected to
             prevent their being deliverable to a higher-layer
             protocol.  One possible reason for discarding such a
             packet could be to free up buffer space.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."

McCloghrie & Kastenholz Standards Track [Page 34] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

     ::= { ifEntry 13 }
 ifInErrors OBJECT-TYPE
     SYNTAX      Counter32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "For packet-oriented interfaces, the number of inbound
             packets that contained errors preventing them from
             being deliverable to a higher-layer protocol.  For
             character-oriented or fixed-length interfaces, the
             number of inbound transmission units that contained
             errors preventing them from being deliverable to a
             higher-layer protocol.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."
     ::= { ifEntry 14 }
 ifInUnknownProtos OBJECT-TYPE
     SYNTAX      Counter32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "For packet-oriented interfaces, the number of packets
             received via the interface which were discarded
             because of an unknown or unsupported protocol.  For
             character-oriented or fixed-length interfaces that
             support protocol multiplexing the number of
             transmission units received via the interface which
             were discarded because of an unknown or unsupported
             protocol.  For any interface that does not support
             protocol multiplexing, this counter will always be 0.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."
     ::= { ifEntry 15 }

McCloghrie & Kastenholz Standards Track [Page 35] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 ifOutOctets OBJECT-TYPE
     SYNTAX      Counter32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The total number of octets transmitted out of the
             interface, including framing characters.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."
     ::= { ifEntry 16 }
 ifOutUcastPkts OBJECT-TYPE
     SYNTAX      Counter32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The total number of packets that higher-level
             protocols requested be transmitted, and which were not
             addressed to a multicast or broadcast address at this
             sub-layer, including those that were discarded or not
             sent.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."
     ::= { ifEntry 17 }
 ifOutNUcastPkts OBJECT-TYPE
     SYNTAX      Counter32
     MAX-ACCESS  read-only
     STATUS      deprecated
     DESCRIPTION
             "The total number of packets that higher-level
             protocols requested be transmitted, and which were
             addressed to a multicast or broadcast address at this
             sub-layer, including those that were discarded or not
             sent.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime.

McCloghrie & Kastenholz Standards Track [Page 36] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

             This object is deprecated in favour of
             ifOutMulticastPkts and ifOutBroadcastPkts."
     ::= { ifEntry 18 }
 ifOutDiscards OBJECT-TYPE
     SYNTAX      Counter32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The number of outbound packets which were chosen to
             be discarded even though no errors had been detected
             to prevent their being transmitted.  One possible
             reason for discarding such a packet could be to free
             up buffer space.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."
     ::= { ifEntry 19 }
 ifOutErrors OBJECT-TYPE
     SYNTAX      Counter32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "For packet-oriented interfaces, the number of
             outbound packets that could not be transmitted because
             of errors.  For character-oriented or fixed-length
             interfaces, the number of outbound transmission units
             that could not be transmitted because of errors.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."
     ::= { ifEntry 20 }
 ifOutQLen OBJECT-TYPE
     SYNTAX      Gauge32
     MAX-ACCESS  read-only
     STATUS      deprecated
     DESCRIPTION
             "The length of the output packet queue (in packets)."
     ::= { ifEntry 21 }

McCloghrie & Kastenholz Standards Track [Page 37] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 ifSpecific OBJECT-TYPE
     SYNTAX      OBJECT IDENTIFIER
     MAX-ACCESS  read-only
     STATUS      deprecated
     DESCRIPTION
             "A reference to MIB definitions specific to the
             particular media being used to realize the interface.
             It is recommended that this value point to an instance
             of a MIB object in the media-specific MIB, i.e., that
             this object have the semantics associated with the
             InstancePointer textual convention defined in RFC
             1903.  In fact, it is recommended that the media-
             specific MIB specify what value ifSpecific should/can
             take for values of ifType.  If no MIB definitions
             specific to the particular media are available, the
             value should be set to the OBJECT IDENTIFIER { 0 0 }."
     ::= { ifEntry 22 }
  1. -
  2. - Extension to the interface table
  3. -
  4. - This table replaces the ifExtnsTable table.
  5. -
 ifXTable        OBJECT-TYPE
     SYNTAX      SEQUENCE OF IfXEntry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
             "A list of interface entries.  The number of entries
             is given by the value of ifNumber.  This table
             contains additional objects for the interface table."
     ::= { ifMIBObjects 1 }
 ifXEntry        OBJECT-TYPE
     SYNTAX      IfXEntry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
             "An entry containing additional management information
             applicable to a particular interface."
     AUGMENTS    { ifEntry }
     ::= { ifXTable 1 }

McCloghrie & Kastenholz Standards Track [Page 38] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 IfXEntry ::=
     SEQUENCE {
         ifName                  DisplayString,
         ifInMulticastPkts       Counter32,
         ifInBroadcastPkts       Counter32,
         ifOutMulticastPkts      Counter32,
         ifOutBroadcastPkts      Counter32,
         ifHCInOctets            Counter64,
         ifHCInUcastPkts         Counter64,
         ifHCInMulticastPkts     Counter64,
         ifHCInBroadcastPkts     Counter64,
         ifHCOutOctets           Counter64,
         ifHCOutUcastPkts        Counter64,
         ifHCOutMulticastPkts    Counter64,
         ifHCOutBroadcastPkts    Counter64,
         ifLinkUpDownTrapEnable  INTEGER,
         ifHighSpeed             Gauge32,
         ifPromiscuousMode       TruthValue,
         ifConnectorPresent      TruthValue,
         ifAlias                 DisplayString,
         ifCounterDiscontinuityTime TimeStamp
     }
 ifName OBJECT-TYPE
     SYNTAX      DisplayString
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The textual name of the interface.  The value of this
             object should be the name of the interface as assigned
             by the local device and should be suitable for use in
             commands entered at the device's `console'.  This
             might be a text name, such as `le0' or a simple port
             number, such as `1', depending on the interface naming
             syntax of the device.  If several entries in the
             ifTable together represent a single interface as named
             by the device, then each will have the same value of
             ifName.  Note that for an agent which responds to SNMP
             queries concerning an interface on some other
             (proxied) device, then the value of ifName for such an
             interface is the proxied device's local name for it.
             If there is no local name, or this object is otherwise
             not applicable, then this object contains a zero-
             length string."
     ::= { ifXEntry 1 }

McCloghrie & Kastenholz Standards Track [Page 39] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 ifInMulticastPkts OBJECT-TYPE
     SYNTAX      Counter32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The number of packets, delivered by this sub-layer to
             a higher (sub-)layer, which were addressed to a
             multicast address at this sub-layer.  For a MAC layer
             protocol, this includes both Group and Functional
             addresses.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."
     ::= { ifXEntry 2 }
 ifInBroadcastPkts OBJECT-TYPE
     SYNTAX      Counter32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The number of packets, delivered by this sub-layer to
             a higher (sub-)layer, which were addressed to a
             broadcast address at this sub-layer.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."
     ::= { ifXEntry 3 }
 ifOutMulticastPkts OBJECT-TYPE
     SYNTAX      Counter32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The total number of packets that higher-level
             protocols requested be transmitted, and which were
             addressed to a multicast address at this sub-layer,
             including those that were discarded or not sent.  For
             a MAC layer protocol, this includes both Group and
             Functional addresses.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."

McCloghrie & Kastenholz Standards Track [Page 40] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

     ::= { ifXEntry 4 }
 ifOutBroadcastPkts OBJECT-TYPE
     SYNTAX      Counter32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The total number of packets that higher-level
             protocols requested be transmitted, and which were
             addressed to a broadcast address at this sub-layer,
             including those that were discarded or not sent.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."
     ::= { ifXEntry 5 }
  1. -
  2. - High Capacity Counter objects. These objects are all
  3. - 64 bit versions of the "basic" ifTable counters. These
  4. - objects all have the same basic semantics as their 32-bit
  5. - counterparts, however, their syntax has been extended
  6. - to 64 bits.
  7. -
 ifHCInOctets OBJECT-TYPE
     SYNTAX      Counter64
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The total number of octets received on the interface,
             including framing characters.  This object is a 64-bit
             version of ifInOctets.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."
     ::= { ifXEntry 6 }

McCloghrie & Kastenholz Standards Track [Page 41] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 ifHCInUcastPkts OBJECT-TYPE
     SYNTAX      Counter64
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The number of packets, delivered by this sub-layer to
             a higher (sub-)layer, which were not addressed to a
             multicast or broadcast address at this sub-layer.
             This object is a 64-bit version of ifInUcastPkts.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."
     ::= { ifXEntry 7 }
 ifHCInMulticastPkts OBJECT-TYPE
     SYNTAX      Counter64
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The number of packets, delivered by this sub-layer to
             a higher (sub-)layer, which were addressed to a
             multicast address at this sub-layer.  For a MAC layer
             protocol, this includes both Group and Functional
             addresses.  This object is a 64-bit version of
             ifInMulticastPkts.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."
     ::= { ifXEntry 8 }
 ifHCInBroadcastPkts OBJECT-TYPE
     SYNTAX      Counter64
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The number of packets, delivered by this sub-layer to
             a higher (sub-)layer, which were addressed to a
             broadcast address at this sub-layer.  This object is a
             64-bit version of ifInBroadcastPkts.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of

McCloghrie & Kastenholz Standards Track [Page 42] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

             ifCounterDiscontinuityTime."
     ::= { ifXEntry 9 }
 ifHCOutOctets OBJECT-TYPE
     SYNTAX      Counter64
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The total number of octets transmitted out of the
             interface, including framing characters.  This object
             is a 64-bit version of ifOutOctets.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."
     ::= { ifXEntry 10 }
 ifHCOutUcastPkts OBJECT-TYPE
     SYNTAX      Counter64
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The total number of packets that higher-level
             protocols requested be transmitted, and which were not
             addressed to a multicast or broadcast address at this
             sub-layer, including those that were discarded or not
             sent.  This object is a 64-bit version of
             ifOutUcastPkts.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."
     ::= { ifXEntry 11 }
 ifHCOutMulticastPkts OBJECT-TYPE
     SYNTAX      Counter64
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The total number of packets that higher-level
             protocols requested be transmitted, and which were
             addressed to a multicast address at this sub-layer,
             including those that were discarded or not sent.  For
             a MAC layer protocol, this includes both Group and
             Functional addresses.  This object is a 64-bit version
             of ifOutMulticastPkts.

McCloghrie & Kastenholz Standards Track [Page 43] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."
     ::= { ifXEntry 12 }
 ifHCOutBroadcastPkts OBJECT-TYPE
     SYNTAX      Counter64
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The total number of packets that higher-level
             protocols requested be transmitted, and which were
             addressed to a broadcast address at this sub-layer,
             including those that were discarded or not sent.  This
             object is a 64-bit version of ifOutBroadcastPkts.
             Discontinuities in the value of this counter can occur
             at re-initialization of the management system, and at
             other times as indicated by the value of
             ifCounterDiscontinuityTime."
     ::= { ifXEntry 13 }
 ifLinkUpDownTrapEnable  OBJECT-TYPE
     SYNTAX      INTEGER { enabled(1), disabled(2) }
     MAX-ACCESS  read-write
     STATUS      current
     DESCRIPTION
             "Indicates whether linkUp/linkDown traps should be
             generated for this interface.
             By default, this object should have the value
             enabled(1) for interfaces which do not operate on
             'top' of any other interface (as defined in the
             ifStackTable), and disabled(2) otherwise."
     ::= { ifXEntry 14 }
 ifHighSpeed OBJECT-TYPE
     SYNTAX      Gauge32
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "An estimate of the interface's current bandwidth in
             units of 1,000,000 bits per second.  If this object
             reports a value of `n' then the speed of the interface
             is somewhere in the range of `n-500,000' to
             `n+499,999'.  For interfaces which do not vary in

McCloghrie & Kastenholz Standards Track [Page 44] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

             bandwidth or for those where no accurate estimation
             can be made, this object should contain the nominal
             bandwidth.  For a sub-layer which has no concept of
             bandwidth, this object should be zero."
     ::= { ifXEntry 15 }
 ifPromiscuousMode  OBJECT-TYPE
     SYNTAX      TruthValue
     MAX-ACCESS  read-write
     STATUS      current
     DESCRIPTION
             "This object has a value of false(2) if this interface
             only accepts packets/frames that are addressed to this
             station.  This object has a value of true(1) when the
             station accepts all packets/frames transmitted on the
             media.  The value true(1) is only legal on certain
             types of media.  If legal, setting this object to a
             value of true(1) may require the interface to be reset
             before becoming effective.
             The value of ifPromiscuousMode does not affect the
             reception of broadcast and multicast packets/frames by
             the interface."
     ::= { ifXEntry 16 }
 ifConnectorPresent   OBJECT-TYPE
     SYNTAX      TruthValue
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "This object has the value 'true(1)' if the interface
             sublayer has a physical connector and the value
             'false(2)' otherwise."
     ::= { ifXEntry 17 }
 ifAlias   OBJECT-TYPE
     SYNTAX      DisplayString (SIZE(0..64))
     MAX-ACCESS  read-write
     STATUS      current
     DESCRIPTION
             "This object is an 'alias' name for the interface as
             specified by a network manager, and provides a non-
             volatile 'handle' for the interface.
             On the first instantiation of an interface, the value
             of ifAlias associated with that interface is the
             zero-length string.  As and when a value is written
             into an instance of ifAlias through a network

McCloghrie & Kastenholz Standards Track [Page 45] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

             management set operation, then the agent must retain
             the supplied value in the ifAlias instance associated
             with the same interface for as long as that interface
             remains instantiated, including across all re-
             initializations/reboots of the network management
             system, including those which result in a change of
             the interface's ifIndex value.
             An example of the value which a network manager might
             store in this object for a WAN interface is the
             (Telco's) circuit number/identifier of the interface.
             Some agents may support write-access only for
             interfaces having particular values of ifType.  An
             agent which supports write access to this object is
             required to keep the value in non-volatile storage,
             but it may limit the length of new values depending on
             how much storage is already occupied by the current
             values for other interfaces."
     ::= { ifXEntry 18 }
 ifCounterDiscontinuityTime OBJECT-TYPE
     SYNTAX      TimeStamp
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The value of sysUpTime on the most recent occasion at
             which any one or more of this interface's counters
             suffered a discontinuity.  The relevant counters are
             the specific instances associated with this interface
             of any Counter32 or Counter64 object contained in the
             ifTable or ifXTable.  If no such discontinuities have
             occurred since the last re-initialization of the local
             management subsystem, then this object contains a zero
             value."
     ::= { ifXEntry 19 }
  1. - The Interface Stack Group
  2. -
  3. - Implementation of this group is mandatory for all systems
  4. -
 ifStackTable  OBJECT-TYPE
      SYNTAX        SEQUENCE OF IfStackEntry
      MAX-ACCESS    not-accessible
      STATUS        current
      DESCRIPTION

McCloghrie & Kastenholz Standards Track [Page 46] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

             "The table containing information on the relationships
             between the multiple sub-layers of network interfaces.
             In particular, it contains information on which sub-
             layers run 'on top of' which other sub-layers, where
             each sub-layer corresponds to a conceptual row in the
             ifTable.  For example, when the sub-layer with ifIndex
             value x runs over the sub-layer with ifIndex value y,
             then this table contains:
               ifStackStatus.x.y=active
             For each ifIndex value, I, which identifies an active
             interface, there are always at least two instantiated
             rows in this table associated with I.  For one of
             these rows, I is the value of ifStackHigherLayer; for
             the other, I is the value of ifStackLowerLayer.  (If I
             is not involved in multiplexing, then these are the
             only two rows associated with I.)
             For example, two rows exist even for an interface
             which has no others stacked on top or below it:
               ifStackStatus.0.x=active
               ifStackStatus.x.0=active "
      ::= { ifMIBObjects 2 }
 ifStackEntry  OBJECT-TYPE
      SYNTAX        IfStackEntry
      MAX-ACCESS    not-accessible
      STATUS        current
      DESCRIPTION
             "Information on a particular relationship between two
             sub-layers, specifying that one sub-layer runs on
             'top' of the other sub-layer.  Each sub-layer
             corresponds to a conceptual row in the ifTable."
      INDEX { ifStackHigherLayer, ifStackLowerLayer }
      ::= { ifStackTable 1 }
 IfStackEntry ::=
     SEQUENCE {
         ifStackHigherLayer  Integer32,
         ifStackLowerLayer   Integer32,
         ifStackStatus       RowStatus
      }

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 ifStackHigherLayer  OBJECT-TYPE
      SYNTAX        Integer32
      MAX-ACCESS    not-accessible
      STATUS        current
      DESCRIPTION
             "The value of ifIndex corresponding to the higher
             sub-layer of the relationship, i.e., the sub-layer
             which runs on 'top' of the sub-layer identified by the
             corresponding instance of ifStackLowerLayer.  If there
             is no higher sub-layer (below the internetwork layer),
             then this object has the value 0."
      ::= { ifStackEntry 1 }
 ifStackLowerLayer  OBJECT-TYPE
      SYNTAX        Integer32
      MAX-ACCESS    not-accessible
      STATUS        current
      DESCRIPTION
             "The value of ifIndex corresponding to the lower sub-
             layer of the relationship, i.e., the sub-layer which
             runs 'below' the sub-layer identified by the
             corresponding instance of ifStackHigherLayer.  If
             there is no lower sub-layer, then this object has the
             value 0."
      ::= { ifStackEntry 2 }
 ifStackStatus  OBJECT-TYPE
     SYNTAX         RowStatus
     MAX-ACCESS     read-create
     STATUS         current
     DESCRIPTION
             "The status of the relationship between two sub-
             layers.
             Changing the value of this object from 'active' to
             'notInService' or 'destroy' will likely have
             consequences up and down the interface stack.  Thus,
             write access to this object is likely to be
             inappropriate for some types of interfaces, and many
             implementations will choose not to support write-
             access for any type of interface."
     ::= { ifStackEntry 3 }
 ifStackLastChange OBJECT-TYPE
     SYNTAX         TimeTicks
     MAX-ACCESS     read-only

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     STATUS         current
     DESCRIPTION
             "The value of sysUpTime at the time of the last change
             of the (whole) interface stack.  A change of the
             interface stack is defined to be any creation,
             deletion, or change in value of any instance of
             ifStackStatus.  If the interface stack has been
             unchanged since the last re-initialization of the
             local network management subsystem, then this object
             contains a zero value."
     ::= { ifMIBObjects 6 }
  1. - Generic Receive Address Table
  2. -
  3. - This group of objects is mandatory for all types of
  4. - interfaces which can receive packets/frames addressed to
  5. - more than one address.
  6. -
  7. - This table replaces the ifExtnsRcvAddr table. The main
  8. - difference is that this table makes use of the RowStatus
  9. - textual convention, while ifExtnsRcvAddr did not.
 ifRcvAddressTable  OBJECT-TYPE
     SYNTAX      SEQUENCE OF IfRcvAddressEntry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
             "This table contains an entry for each address
             (broadcast, multicast, or uni-cast) for which the
             system will receive packets/frames on a particular
             interface, except as follows:
  1. for an interface operating in promiscuous mode,

entries are only required for those addresses for

             which the system would receive frames were it not
             operating in promiscuous mode.
  1. for 802.5 functional addresses, only one entry is

required, for the address which has the functional

             address bit ANDed with the bit mask of all functional
             addresses for which the interface will accept frames.
             A system is normally able to use any unicast address
             which corresponds to an entry in this table as a
             source address."
     ::= { ifMIBObjects 4 }

McCloghrie & Kastenholz Standards Track [Page 49] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 ifRcvAddressEntry  OBJECT-TYPE
     SYNTAX      IfRcvAddressEntry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
             "A list of objects identifying an address for which
             the system will accept packets/frames on the
             particular interface identified by the index value
             ifIndex."
     INDEX  { ifIndex, ifRcvAddressAddress }
     ::= { ifRcvAddressTable 1 }
 IfRcvAddressEntry ::=
     SEQUENCE {
         ifRcvAddressAddress   PhysAddress,
         ifRcvAddressStatus    RowStatus,
         ifRcvAddressType      INTEGER
     }
 ifRcvAddressAddress OBJECT-TYPE
     SYNTAX      PhysAddress
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
             "An address for which the system will accept
             packets/frames on this entry's interface."
     ::= { ifRcvAddressEntry 1 }
 ifRcvAddressStatus OBJECT-TYPE
     SYNTAX      RowStatus
     MAX-ACCESS  read-create
     STATUS      current
     DESCRIPTION
             "This object is used to create and delete rows in the
             ifRcvAddressTable."
     ::= { ifRcvAddressEntry 2 }
 ifRcvAddressType OBJECT-TYPE
     SYNTAX      INTEGER {
                     other(1),
                     volatile(2),
                     nonVolatile(3)
                 }
     MAX-ACCESS  read-create
     STATUS      current

McCloghrie & Kastenholz Standards Track [Page 50] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

     DESCRIPTION
             "This object has the value nonVolatile(3) for those
             entries in the table which are valid and will not be
             deleted by the next restart of the managed system.
             Entries having the value volatile(2) are valid and
             exist, but have not been saved, so that will not exist
             after the next restart of the managed system.  Entries
             having the value other(1) are valid and exist but are
             not classified as to whether they will continue to
             exist after the next restart."
     DEFVAL  { volatile }
     ::= { ifRcvAddressEntry 3 }
  1. - definition of interface-related traps.
 linkDown NOTIFICATION-TYPE
         OBJECTS { ifIndex, ifAdminStatus, ifOperStatus }
         STATUS  current
         DESCRIPTION
             "A linkDown trap signifies that the SNMPv2 entity,
             acting in an agent role, has detected that the
             ifOperStatus object for one of its communication links
             is about to enter the down state from some other state
             (but not from the notPresent state).  This other state
             is indicated by the included value of ifOperStatus."
     ::= { snmpTraps 3 }
 linkUp NOTIFICATION-TYPE
         OBJECTS { ifIndex, ifAdminStatus, ifOperStatus }
         STATUS  current
         DESCRIPTION
             "A linkDown trap signifies that the SNMPv2 entity,
             acting in an agent role, has detected that the
             ifOperStatus object for one of its communication links
             left the down state and transitioned into some other
             state (but not into the notPresent state).  This other
             state is indicated by the included value of
             ifOperStatus."
     ::= { snmpTraps 4 }
  1. - conformance information
 ifConformance OBJECT IDENTIFIER ::= { ifMIB 2 }
 ifGroups      OBJECT IDENTIFIER ::= { ifConformance 1 }
 ifCompliances OBJECT IDENTIFIER ::= { ifConformance 2 }

McCloghrie & Kastenholz Standards Track [Page 51] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

  1. - compliance statements
 ifCompliance2 MODULE-COMPLIANCE
     STATUS  current
     DESCRIPTION
             "The compliance statement for SNMPv2 entities which
             have network interfaces."
     MODULE  -- this module
         MANDATORY-GROUPS { ifGeneralInformationGroup, ifStackGroup2,
                            ifCounterDiscontinuityGroup }
         GROUP       ifFixedLengthGroup
         DESCRIPTION
             "This group is mandatory for all network interfaces
             which are character-oriented or transmit data in
             fixed-length transmission units."
         GROUP       ifHCFixedLengthGroup
         DESCRIPTION
             "This group is mandatory only for those network
             interfaces which are character-oriented or transmit
             data in fixed-length transmission units, and for which
             the value of the corresponding instance of ifSpeed is
             greater than 20,000,000 bits/second."
         GROUP       ifPacketGroup
         DESCRIPTION
             "This group is mandatory for all network interfaces
             which are packet-oriented."
         GROUP       ifHCPacketGroup
         DESCRIPTION
             "This group is mandatory only for those network
             interfaces which are packet-oriented and for which the
             value of the corresponding instance of ifSpeed is
             greater than 650,000,000 bits/second."
         GROUP       ifRcvAddressGroup
         DESCRIPTION
             "The applicability of this group MUST be defined by
             the media-specific MIBs.  Media-specific MIBs must
             define the exact meaning, use, and semantics of the
             addresses in this group."

McCloghrie & Kastenholz Standards Track [Page 52] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

         OBJECT      ifLinkUpDownTrapEnable
         MIN-ACCESS  read-only
         DESCRIPTION
             "Write access is not required."
         OBJECT      ifPromiscuousMode
         MIN-ACCESS  read-only
         DESCRIPTION
             "Write access is not required."
         OBJECT      ifStackStatus
         SYNTAX      INTEGER { active(1) } -- subset of RowStatus
         MIN-ACCESS  read-only
         DESCRIPTION
             "Write access is not required, and only one of the six
             enumerated values for the RowStatus textual convention
             need be supported, specifically: active(1)."
         OBJECT       ifAdminStatus
         SYNTAX       INTEGER { up(1), down(2) }
         MIN-ACCESS   read-only
         DESCRIPTION
             "Write access is not required, nor is support for the
             value testing(3)."
         OBJECT       ifAlias
         MIN-ACCESS   read-only
         DESCRIPTION
             "Write access is not required."
     ::= { ifCompliances 2 }
  1. - units of conformance
 ifGeneralInformationGroup    OBJECT-GROUP
     OBJECTS { ifIndex, ifDescr, ifType, ifSpeed, ifPhysAddress,
               ifAdminStatus, ifOperStatus, ifLastChange,
               ifLinkUpDownTrapEnable, ifConnectorPresent,
               ifHighSpeed, ifName, ifNumber, ifAlias,
               ifTableLastChange }
     STATUS  current
     DESCRIPTION
             "A collection of objects providing information
             applicable to all network interfaces."
     ::= { ifGroups 10 }
  1. - the following five groups are mutually exclusive; at most
  2. - one of these groups is implemented for any interface

McCloghrie & Kastenholz Standards Track [Page 53] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 ifFixedLengthGroup    OBJECT-GROUP
     OBJECTS { ifInOctets, ifOutOctets, ifInUnknownProtos,
               ifInErrors, ifOutErrors }
     STATUS  current
     DESCRIPTION
             "A collection of objects providing information
             specific to non-high speed (non-high speed interfaces
             transmit and receive at speeds less than or equal to
             20,000,000 bits/second) character-oriented or fixed-
             length-transmission network interfaces."
     ::= { ifGroups 2 }
 ifHCFixedLengthGroup    OBJECT-GROUP
     OBJECTS { ifHCInOctets, ifHCOutOctets,
               ifInOctets, ifOutOctets, ifInUnknownProtos,
               ifInErrors, ifOutErrors }
     STATUS  current
     DESCRIPTION
             "A collection of objects providing information
             specific to high speed (greater than 20,000,000
             bits/second) character-oriented or fixed-length-
             transmission network interfaces."
     ::= { ifGroups 3 }
 ifPacketGroup    OBJECT-GROUP
     OBJECTS { ifInOctets, ifOutOctets, ifInUnknownProtos,
               ifInErrors, ifOutErrors,
               ifMtu, ifInUcastPkts, ifInMulticastPkts,
               ifInBroadcastPkts, ifInDiscards,
               ifOutUcastPkts, ifOutMulticastPkts,
               ifOutBroadcastPkts, ifOutDiscards,
               ifPromiscuousMode }
     STATUS  current
     DESCRIPTION
             "A collection of objects providing information
             specific to non-high speed (non-high speed interfaces
             transmit and receive at speeds less than or equal to
             20,000,000 bits/second) packet-oriented network
             interfaces."
     ::= { ifGroups 4 }
 ifHCPacketGroup    OBJECT-GROUP
     OBJECTS { ifHCInOctets, ifHCOutOctets,
               ifInOctets, ifOutOctets, ifInUnknownProtos,
               ifInErrors, ifOutErrors,
               ifMtu, ifInUcastPkts, ifInMulticastPkts,
               ifInBroadcastPkts, ifInDiscards,
               ifOutUcastPkts, ifOutMulticastPkts,

McCloghrie & Kastenholz Standards Track [Page 54] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

               ifOutBroadcastPkts, ifOutDiscards,
               ifPromiscuousMode }
     STATUS  current
     DESCRIPTION
             "A collection of objects providing information
             specific to high speed (greater than 20,000,000
             bits/second but less than or equal to 650,000,000
             bits/second) packet-oriented network interfaces."
     ::= { ifGroups 5 }
 ifVHCPacketGroup    OBJECT-GROUP
     OBJECTS { ifHCInUcastPkts, ifHCInMulticastPkts,
               ifHCInBroadcastPkts, ifHCOutUcastPkts,
               ifHCOutMulticastPkts, ifHCOutBroadcastPkts,
               ifHCInOctets, ifHCOutOctets,
               ifInOctets, ifOutOctets, ifInUnknownProtos,
               ifInErrors, ifOutErrors,
               ifMtu, ifInUcastPkts, ifInMulticastPkts,
               ifInBroadcastPkts, ifInDiscards,
               ifOutUcastPkts, ifOutMulticastPkts,
               ifOutBroadcastPkts, ifOutDiscards,
               ifPromiscuousMode }
     STATUS  current
     DESCRIPTION
             "A collection of objects providing information
             specific to higher speed (greater than 650,000,000
             bits/second) packet-oriented network interfaces."
     ::= { ifGroups 6 }
 ifRcvAddressGroup    OBJECT-GROUP
     OBJECTS { ifRcvAddressStatus, ifRcvAddressType }
     STATUS  current
     DESCRIPTION
             "A collection of objects providing information on the
             multiple addresses which an interface receives."
     ::= { ifGroups 7 }
 ifStackGroup2    OBJECT-GROUP
     OBJECTS { ifStackStatus, ifStackLastChange }
     STATUS  current
     DESCRIPTION
             "A collection of objects providing information on the
             layering of MIB-II interfaces."
     ::= { ifGroups 11 }
 ifCounterDiscontinuityGroup  OBJECT-GROUP
     OBJECTS { ifCounterDiscontinuityTime }
     STATUS  current

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     DESCRIPTION
             "A collection of objects providing information
             specific to interface counter discontinuities."
     ::= { ifGroups 13 }
  1. - Deprecated Definitions - Objects
  1. -
  2. - The Interface Test Table
  3. -
  4. - This group of objects is optional. However, a media-specific
  5. - MIB may make implementation of this group mandatory.
  6. -
  7. - This table replaces the ifExtnsTestTable
  8. -
 ifTestTable   OBJECT-TYPE
     SYNTAX      SEQUENCE OF IfTestEntry
     MAX-ACCESS  not-accessible
     STATUS      deprecated
     DESCRIPTION
             "This table contains one entry per interface.  It
             defines objects which allow a network manager to
             instruct an agent to test an interface for various
             faults.  Tests for an interface are defined in the
             media-specific MIB for that interface.  After invoking
             a test, the object ifTestResult can be read to
             determine the outcome.  If an agent can not perform
             the test, ifTestResult is set to so indicate.  The
             object ifTestCode can be used to provide further
             test-specific or interface-specific (or even
             enterprise-specific) information concerning the
             outcome of the test.  Only one test can be in progress
             on each interface at any one time.  If one test is in
             progress when another test is invoked, the second test
             is rejected.  Some agents may reject a test when a
             prior test is active on another interface.
             Before starting a test, a manager-station must first
             obtain 'ownership' of the entry in the ifTestTable for
             the interface to be tested.  This is accomplished with
             the ifTestId and ifTestStatus objects as follows:
          try_again:
              get (ifTestId, ifTestStatus)
              while (ifTestStatus != notInUse)
                  /*

McCloghrie & Kastenholz Standards Track [Page 56] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

  • Loop while a test is running or some other
  • manager is configuring a test.
  • /

short delay

                  get (ifTestId, ifTestStatus)
              }
              /*
               * Is not being used right now -- let's compete
               * to see who gets it.
               */
              lock_value = ifTestId
              if ( set(ifTestId = lock_value, ifTestStatus = inUse,
                       ifTestOwner = 'my-IP-address') == FAILURE)
                  /*
                   * Another manager got the ifTestEntry -- go
                   * try again
                   */
                  goto try_again;
              /*
               * I have the lock
               */
              set up any test parameters.
              /*
               * This starts the test
               */
              set(ifTestType = test_to_run);
              wait for test completion by polling ifTestResult
              when test completes, agent sets ifTestResult
                   agent also sets ifTestStatus = 'notInUse'
              retrieve any additional test results, and ifTestId
              if (ifTestId == lock_value+1) results are valid
            A manager station first retrieves the value of the
            appropriate ifTestId and ifTestStatus objects,
            periodically repeating the retrieval if necessary,
            until the value of ifTestStatus is 'notInUse'.  The
            manager station then tries to set the same ifTestId
            object to the value it just retrieved, the same
            ifTestStatus object to 'inUse', and the corresponding
            ifTestOwner object to a value indicating itself.  If

McCloghrie & Kastenholz Standards Track [Page 57] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

            the set operation succeeds then the manager has
            obtained ownership of the ifTestEntry, and the value of
            the ifTestId object is incremented by the agent (per
            the semantics of TestAndIncr).  Failure of the set
            operation indicates that some other manager has
            obtained ownership of the ifTestEntry.
            Once ownership is obtained, any test parameters can be
            setup, and then the test is initiated by setting
            ifTestType.  On completion of the test, the agent sets
            ifTestStatus to 'notInUse'.  Once this occurs, the
            manager can retrieve the results.  In the (rare) event
            that the invocation of tests by two network managers
            were to overlap, then there would be a possibility that
            the first test's results might be overwritten by the
            second test's results prior to the first results being
            read.  This unlikely circumstance can be detected by a
            network manager retrieving ifTestId at the same time as
            retrieving the test results, and ensuring that the
            results are for the desired request.
            If ifTestType is not set within an abnormally long
            period of time after ownership is obtained, the agent
            should time-out the manager, and reset the value of the
            ifTestStatus object back to 'notInUse'.  It is
            suggested that this time-out period be 5 minutes.
            In general, a management station must not retransmit a
            request to invoke a test for which it does not receive
            a response; instead, it properly inspects an agent's
            MIB to determine if the invocation was successful.
            Only if the invocation was unsuccessful, is the
            invocation request retransmitted.
            Some tests may require the interface to be taken off-
            line in order to execute them, or may even require the
            agent to reboot after completion of the test.  In these
            circumstances, communication with the management
            station invoking the test may be lost until after
            completion of the test.  An agent is not required to
            support such tests.  However, if such tests are
            supported, then the agent should make every effort to
            transmit a response to the request which invoked the
            test prior to losing communication.  When the agent is
            restored to normal service, the results of the test are
            properly made available in the appropriate objects.
            Note that this requires that the ifIndex value assigned
            to an interface must be unchanged even if the test

McCloghrie & Kastenholz Standards Track [Page 58] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

            causes a reboot.  An agent must reject any test for
            which it cannot, perhaps due to resource constraints,
            make available at least the minimum amount of
            information after that test completes."
     ::= { ifMIBObjects 3 }
 ifTestEntry OBJECT-TYPE
     SYNTAX       IfTestEntry
     MAX-ACCESS   not-accessible
     STATUS       deprecated
     DESCRIPTION
             "An entry containing objects for invoking tests on an
             interface."
     AUGMENTS  { ifEntry }
     ::= { ifTestTable 1 }
 IfTestEntry ::=
     SEQUENCE {
         ifTestId           TestAndIncr,
         ifTestStatus       INTEGER,
         ifTestType         AutonomousType,
         ifTestResult       INTEGER,
         ifTestCode         OBJECT IDENTIFIER,
         ifTestOwner        OwnerString
     }
 ifTestId         OBJECT-TYPE
     SYNTAX       TestAndIncr
     MAX-ACCESS   read-write
     STATUS       deprecated
     DESCRIPTION
             "This object identifies the current invocation of the
             interface's test."
     ::= { ifTestEntry 1 }
 ifTestStatus     OBJECT-TYPE
     SYNTAX       INTEGER { notInUse(1), inUse(2) }
     MAX-ACCESS   read-write
     STATUS       deprecated
     DESCRIPTION
             "This object indicates whether or not some manager
             currently has the necessary 'ownership' required to
             invoke a test on this interface.  A write to this
             object is only successful when it changes its value
             from 'notInUse(1)' to 'inUse(2)'.  After completion of
             a test, the agent resets the value back to
             'notInUse(1)'."
     ::= { ifTestEntry 2 }

McCloghrie & Kastenholz Standards Track [Page 59] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 ifTestType       OBJECT-TYPE
     SYNTAX       AutonomousType
     MAX-ACCESS   read-write
     STATUS       deprecated
     DESCRIPTION
             "A control variable used to start and stop operator-
             initiated interface tests.  Most OBJECT IDENTIFIER
             values assigned to tests are defined elsewhere, in
             association with specific types of interface.
             However, this document assigns a value for a full-
             duplex loopback test, and defines the special meanings
             of the subject identifier:
                 noTest  OBJECT IDENTIFIER ::= { 0 0 }
             When the value noTest is written to this object, no
             action is taken unless a test is in progress, in which
             case the test is aborted.  Writing any other value to
             this object is only valid when no test is currently in
             progress, in which case the indicated test is
             initiated.
             When read, this object always returns the most recent
             value that ifTestType was set to.  If it has not been
             set since the last initialization of the network
             management subsystem on the agent, a value of noTest
             is returned."
     ::= { ifTestEntry 3 }
 ifTestResult  OBJECT-TYPE
     SYNTAX       INTEGER {
                      none(1),          -- no test yet requested
                      success(2),
                      inProgress(3),
                      notSupported(4),
                      unAbleToRun(5),   -- due to state of system
                      aborted(6),
                      failed(7)
                  }
     MAX-ACCESS   read-only
     STATUS       deprecated
     DESCRIPTION
             "This object contains the result of the most recently
             requested test, or the value none(1) if no tests have
             been requested since the last reset.  Note that this
             facility provides no provision for saving the results
             of one test when starting another, as could be
             required if used by multiple managers concurrently."

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     ::= { ifTestEntry 4 }
 ifTestCode  OBJECT-TYPE
     SYNTAX       OBJECT IDENTIFIER
     MAX-ACCESS   read-only
     STATUS       deprecated
     DESCRIPTION
             "This object contains a code which contains more
             specific information on the test result, for example
             an error-code after a failed test.  Error codes and
             other values this object may take are specific to the
             type of interface and/or test.  The value may have the
             semantics of either the AutonomousType or
             InstancePointer textual conventions as defined in RFC
             1903.  The identifier:
                 testCodeUnknown  OBJECT IDENTIFIER ::= { 0 0 }
             is defined for use if no additional result code is
             available."
     ::= { ifTestEntry 5 }
 ifTestOwner      OBJECT-TYPE
     SYNTAX       OwnerString
     MAX-ACCESS   read-write
     STATUS       deprecated
     DESCRIPTION
             "The entity which currently has the 'ownership'
             required to invoke a test on this interface."
     ::= { ifTestEntry 6 }
  1. - Deprecated Definitions - Groups
 ifGeneralGroup    OBJECT-GROUP
     OBJECTS { ifDescr, ifType, ifSpeed, ifPhysAddress,
               ifAdminStatus, ifOperStatus, ifLastChange,
               ifLinkUpDownTrapEnable, ifConnectorPresent,
               ifHighSpeed, ifName }
     STATUS  deprecated
     DESCRIPTION
             "A collection of objects deprecated in favour of
             ifGeneralInformationGroup."
     ::= { ifGroups 1 }
 ifTestGroup    OBJECT-GROUP
     OBJECTS { ifTestId, ifTestStatus, ifTestType,

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               ifTestResult, ifTestCode, ifTestOwner }
     STATUS  deprecated
     DESCRIPTION
             "A collection of objects providing the ability to
             invoke tests on an interface."
     ::= { ifGroups 8 }
 ifStackGroup    OBJECT-GROUP
     OBJECTS { ifStackStatus }
     STATUS  deprecated
     DESCRIPTION
             "The previous collection of objects providing
             information on the layering of MIB-II interfaces."
     ::= { ifGroups 9 }
 ifOldObjectsGroup    OBJECT-GROUP
     OBJECTS { ifInNUcastPkts, ifOutNUcastPkts,
               ifOutQLen, ifSpecific }
     STATUS  deprecated
     DESCRIPTION
             "The collection of objects deprecated from the
             original MIB-II interfaces group."
     ::= { ifGroups 12 }
  1. - Deprecated Definitions - Compliance
 ifCompliance MODULE-COMPLIANCE
     STATUS  deprecated
     DESCRIPTION
             "The previous compliance statement for SNMPv2 entities
             which have network interfaces."
     MODULE  -- this module
         MANDATORY-GROUPS { ifGeneralGroup, ifStackGroup }
         GROUP       ifFixedLengthGroup
         DESCRIPTION
             "This group is mandatory for all network interfaces
             which are character-oriented or transmit data in
             fixed-length transmission units."
         GROUP       ifHCFixedLengthGroup
         DESCRIPTION
             "This group is mandatory only for those network
             interfaces which are character-oriented or transmit

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             data in fixed-length transmission units, and for which
             the value of the corresponding instance of ifSpeed is
             greater than 20,000,000 bits/second."
         GROUP       ifPacketGroup
         DESCRIPTION
             "This group is mandatory for all network interfaces
             which are packet-oriented."
         GROUP       ifHCPacketGroup
         DESCRIPTION
             "This group is mandatory only for those network
             interfaces which are packet-oriented and for which the
             value of the corresponding instance of ifSpeed is
             greater than 650,000,000 bits/second."
         GROUP       ifTestGroup
         DESCRIPTION
             "This group is optional.  Media-specific MIBs which
             require interface tests are strongly encouraged to use
             this group for invoking tests and reporting results.
             A medium specific MIB which has mandatory tests may
             make implementation of this group mandatory."
         GROUP       ifRcvAddressGroup
         DESCRIPTION
             "The applicability of this group MUST be defined by
             the media-specific MIBs.  Media-specific MIBs must
             define the exact meaning, use, and semantics of the
             addresses in this group."
         OBJECT      ifLinkUpDownTrapEnable
         MIN-ACCESS  read-only
         DESCRIPTION
             "Write access is not required."
         OBJECT      ifPromiscuousMode
         MIN-ACCESS  read-only
         DESCRIPTION
             "Write access is not required."
         OBJECT      ifStackStatus
         SYNTAX      INTEGER { active(1) } -- subset of RowStatus
         MIN-ACCESS  read-only
         DESCRIPTION
             "Write access is not required, and only one of the six
             enumerated values for the RowStatus textual convention
             need be supported, specifically: active(1)."

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         OBJECT       ifAdminStatus
         SYNTAX       INTEGER { up(1), down(2) }
         MIN-ACCESS   read-only
         DESCRIPTION
             "Write access is not required, nor is support for the
             value testing(3)."
     ::= { ifCompliances 1 }
 END

7. Acknowledgements

 This memo has been produced by the IETF's Interfaces MIB working-
 group.
 The original proposal evolved from conversations and discussions with
 many people, including at least the following: Fred Baker, Ted
 Brunner, Chuck Davin, Jeremy Greene, Marshall Rose, Kaj Tesink, and
 Dean Throop.

8. References

 [1]  Case, J., McCloghrie, K., Rose, M., and
      S. Waldbusser, "Structure of Management Information for
      version 2 of the Simple Network Management Protocol
      (SNMPv2)", RFC 1902, January 1996.
 [2]  Case, J., McCloghrie, K., Rose, M., and
      S. Waldbusser, "Textual Conventions for version 2 of the
      Simple Network Management Protocol (SNMPv2)", RFC 1903,
      January 1996.
 [3]  Case, J., McCloghrie, K., Rose, M., and
      S. Waldbusser, "Protocol Operations for version 2 of the
      Simple Network Management Protocol (SNMPv2)", RFC 1905,
      January 1996.
 [4]  McCloghrie, K., and M. Rose, "Management Information Base for
      Network Management of TCP/IP-based internets - MIB-II", STD
      17, RFC 1213, March 1991.
 [5]  Case, J., Fedor, M., Schoffstall, M., and J. Davin, "Simple
      Network Management Protocol", STD 15, RFC 1157, May 1990.
 [6]  Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981.
 [7]  McCloghrie, K., "Extensions to the Generic-Interface MIB", RFC
      1229, May 1991.

McCloghrie & Kastenholz Standards Track [Page 64] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

 [8]  ATM Forum Technical Committee, "LAN Emulation Client
      Management: Version 1.0 Specification", af-lane-0044.000, ATM
      Forum, September 1995.
 [9]  Stewart, B., "Definitions of Managed Objects for Character
      Stream Devices using SMIv2", RFC 1658, July 1994.
 [10] Bradner, S., "Key words for use in RFCs to Indicate
      Requirements Levels", RFC 2119, March 1997.

9. Security Considerations

 This MIB contains both readable objects whose values provide the
 number and status of a device's network interfaces, and write-able
 objects which allow an administrator to control the interfaces and to
 perform tests on the interfaces.  Unauthorized access to the readable
 objects is relatively innocuous.  Unauthorized access to the write-
 able objects could cause a denial of service, or in combination with
 other (e.g., physical) security breaches, could cause unauthorized
 connectivity to a device.

10. Authors' Addresses

 Keith McCloghrie
 Cisco Systems, Inc.
 170 West Tasman Drive
 San Jose, CA  95134-1706
 Phone: 408-526-5260
 EMail: kzm@cisco.com
 Frank Kastenholz
 FTP Software
 2 High Street
 North Andover, Mass. USA 01845
 Phone: 508-685-4000
 EMail: kasten@ftp.com

McCloghrie & Kastenholz Standards Track [Page 65] RFC 2233 Interfaces Group MIB using SMIv2 November 1997

11. Full Copyright Statement

 Copyright (C) The Internet Society (1997).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

McCloghrie & Kastenholz Standards Track [Page 66]

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