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RFC 1156

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Management Information Base for network management of TCP/IP-based internets

Part 1 of 3, p. 1 to 25
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Obsoletes:    1066


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Network Working Group                                     K. McCloghrie
Request For Comments:  1156                          Hughes LAN Systems
Obsoletes:  RFC 1066                                            M. Rose
                                      Performance Systems International
                                                               May 1990


           Management Information Base for Network Management
                       of TCP/IP-based internets

Table of Contents

   1. Status of this Memo ...................................   1
   2. IAB Policy Statement ..................................   2
   3. Introduction ..........................................   2
   4. Objects ...............................................   6
   4.1 Object Groups ........................................   6
   4.2 Format of Definitions ................................   7
   5. Object Definitions ....................................   8
   5.1 The System Group .....................................   9
   5.2 The Interfaces Group .................................  11
   5.2.1 The Interfaces Table ...............................  11
   5.3 The Address Translation Group ........................  23
   5.4 The IP Group .........................................  26
   5.4.1 The IP Address Table ...............................  34
   5.4.2 The IP Routing Table ...............................  36
   5.5 The ICMP Group .......................................  43
   5.6 The TCP Group ........................................  53
   5.7 The UDP Group ........................................  62
   5.8 The EGP Group ........................................  64
   5.8.1 The EGP Neighbor Table .............................  65
   6. Definitions ...........................................  68
   7. Acknowledgements ......................................  89
   8. References ............................................  90
   9. Security Considerations................................  91
   10. Authors' Addresses....................................  91

1.  Status of this Memo

   This RFC is a re-release of RFC 1066, with a changed "Status of this
   Memo", "IAB Policy Statement", and "Introduction" sections plus a few
   minor typographical corrections.  The technical content of the
   document is unchanged from RFC 1066.

   This memo provides the initial version of the Management Information
   Base (MIB) for use with network management protocols in TCP/IP-based
   internets in the short-term.  In particular, together with its
   companion memos which describe the structure of management

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   information along with the initial network management protocol, these
   documents provide a simple, workable architecture and system for
   managing TCP/IP-based internets and in particular the Internet.

   This memo specifies a Standard Protocol for the Internet community.
   TCP/IP implementations in the Internet which are network manageable
   are expected to adopt and implement this specification.

   The Internet Activities Board recommends that all IP and TCP
   implementations be network manageable.  This implies implementation
   of the Internet MIB (RFC-1156) and at least one of the two
   recommended management protocols SNMP (RFC-1157) or CMOT (RFC-1095).
   It should be noted that, at this time, SNMP is a full Internet
   standard and CMOT is a draft standard.  See also the Host and Gateway
   Requirements RFCs for more specific information on the applicability
   of this standard.

   Please refer to the latest edition of the "IAB Official Protocol
   Standards" RFC for current information on the state and status of
   standard Internet protocols.

   Distribution of this memo is unlimited.

2.  IAB Policy Statement

   This MIB specification is the first edition of an evolving document
   defining variables needed for monitoring and control of various
   components of the Internet.  Not all groups of defined variables are
   mandatory for all Internet components.

   For example, the EGP group is mandatory for gateways using EGP but
   not for hosts which should not be running EGP.  Similarly, the TCP
   group is mandatory for hosts running TCP but not for gateways which
   aren't running it.  What IS mandatory, however, is that all variables
   of a group be supported if any element of the group is supported.

   It is expected that additional MIB groups and variables will be
   defined over time to accommodate the monitoring and control needs of
   new or changing components of the Internet.  The responsible working
   group(s) will continue to refine this specification.

3.  Introduction

   As reported in RFC 1052, IAB Recommendations for the Development of
   Internet Network Management Standards [1], the Internet Activities
   Board has directed the Internet Engineering Task Force (IETF) to
   create two new working groups in the area of network management.  One
   group was charged with the further specification and definition of

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   elements to be included in the Management Information Base.  The
   other was charged with defining the modifications to the Simple
   Network Management Protocol (SNMP) to accommodate the short-term
   needs of the network vendor and operator communities.  In the long-
   term, the use of the OSI network management framework was to be
   examined using the ISO CMIS/CMIP [2,3] framework as a basis.  Two
   documents were produced to define the management information:  RFC
   1065, which defined the Structure of Management Information (SMI)
   [4], and RFC 1066, which defined the Management Information Base
   (MIB) [5].  Both of these documents were designed so as to be
   compatible with both the SNMP and the OSI network management
   framework.

   This strategy was quite successful in the short-term: Internet-based
   network management technology was fielded, by both the research and
   commercial communities, within a few months.  As a result of this,
   portions of the Internet community became network manageable in a
   timely fashion.

   As reported in RFC 1109, Report of the Second Ad Hoc Network
   Management Review Group [6], the requirements of the SNMP and the OSI
   network management frameworks were more different than anticipated.
   As such, the requirement for compatibility between the SMI/MIB and
   both frameworks was suspended.

   The IAB has designated the SNMP, SMI, and the initial Internet MIB to
   be full "Standard Protocols" with "Recommended" status.  By this
   action, the IAB recommends that all IP and TCP implementations be
   network manageable and that the implementations that are network
   manageable are expected to adopt and implement the SMI, MIB, and
   SNMP.

   As such, the current network management framework for TCP/IP- based
   internets consists of:  Structure and Identification of Management
   Information for TCP/IP-based Internets, which describes how managed
   objects contained in the MIB are defined as set forth in RFC 1155
   [7]; Management Information Base for Network Management of TCP/IP-
   based Internets, which describes the managed objects contained in the
   MIB as set forth in this memo; and, the Simple Network Management
   Protocol, which defines the protocol used to manage these objects, as
   set forth in RFC 1157 [8].

   The IAB also urged the working groups to be "extremely sensitive to
   the need to keep SNMP simple," and recommends that the MIB working
   group take as its starting inputs the MIB definitions found in the
   High-Level Entity Management Systems (HEMS) RFC 1024 [9], the initial
   SNMP specification [10], and the CMIS/CMIP memos [11,12].

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   Thus, the list of managed objects defined here, has been derived by
   taking only those elements which are considered essential.  Since
   such elements are essential, there is no need to allow the
   implementation of individual objects, to be optional.  Rather, all
   compliant implementations will contain all applicable (see below)
   objects defined in this memo.

   This approach of taking only the essential objects is NOT
   restrictive, since the SMI defined in the companion memo provides
   three extensibility mechanisms:  one, the addition of new standard
   objects through the definitions of new versions of the MIB; two, the
   addition of widely-available but non-standard objects through the
   multilateral subtree; and three, the addition of private objects
   through the enterprises subtree. Such additional objects can not only
   be used for vendor-specific elements, but also for experimentation as
   required to further the knowledge of which other objects are
   essential.

   The primary criterion for being considered essential was for an
   object to be contained in all of the above referenced MIB
   definitions.  A few other objects have been included, but only if the
   MIB working group believed they are truly essential.  The detailed
   list of criteria against which potential inclusions in this (initial)
   MIB were considered, was:

      1) An object needed to be essential for either fault or
         configuration management.

      2) Only weak control objects were permitted (by weak, it
         is meant that tampering with them can do only limited
         damage).  This criterion reflects the fact that the
         current management protocols are not sufficiently secure
         to do more powerful control operations.

      3) Evidence of current use and utility was required.

      4) An attempt was made to limit the number of objects to
         about 100 to make it easier for vendors to fully
         instrument their software.

      5) To avoid redundant variables, it was required that no
         object be included that can be derived from others in the
         MIB.

      6) Implementation specific objects (e.g., for BSD UNIX)
         were excluded.

      7) It was agreed to avoid heavily instrumenting critical

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         sections of code.  The general guideline was one counter
         per critical section per layer.

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4.  Objects

   Managed objects are accessed via a virtual information store, termed
   the Management Information Base or MIB.  Objects in the MIB are
   defined using Abstract Syntax Notation One (ASN.1) [13].

   The mechanisms used for describing these objects are specified in the
   companion memo.  In particular, each object has a name, a syntax, and
   an encoding.  The name is an object identifier, an administratively
   assigned name, which specifies an object type.  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 OBJECT DESCRIPTOR, to also
   refer to the object type.

   The syntax of an object type defines the abstract data structure
   corresponding to that object type.  The ASN.1 language is used for
   this purpose.  However, the companion memo purposely restricts the
   ASN.1 constructs which may be used.  These restrictions are
   explicitly made for simplicity.

   The encoding of an object type is simply how that object type is
   represented using the object type's syntax.  Implicitly tied to the
   notion of an object type's syntax and encoding is how the object type
   is represented when being transmitted on the network.  This memo
   specifies the use of the basic encoding rules of ASN.1 [14].

4.1.  Object Groups

   Since this list of managed objects contains only the essential
   elements, there is no need to allow individual objects to be
   optional.  Rather, the objects are arranged into the following
   groups:

                  - System
                  - Interfaces
                  - Address Translation
                  - IP
                  - ICMP
                  - TCP
                  - UDP
                  - EGP

   There are two reasons for defining these groups:  one, to provide a
   means of assigning object identifiers; two, to provide a method for
   implementations of managed agents to know which objects they must
   implement.  This method is as follows: if the semantics of a group is
   applicable to an implementation, then it must implement all objects

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   in that group.  For example, an implementation must implement the EGP
   group if and only if it implements the EGP protocol.

4.2.  Format of Definitions

   The next section contains the specification of all object types
   contained in the MIB. Following the conventions of the companion
   memo, the object types are defined using the following fields:

          OBJECT:
          -------
               A textual name, termed the OBJECT DESCRIPTOR, for the
               object type, along with its corresponding OBJECT
               IDENTIFIER.

          Syntax:
               The abstract syntax for the object type, presented using
               ASN.1.  This must resolve to an instance of the ASN.1
               type ObjectSyntax defined in the SMI.

          Definition:
               A textual description of the semantics of the object
               type.  Implementations should ensure that their
               interpretation of the object type fulfills this
               definition since this MIB is intended for use in multi-
               vendor environments.  As such it is vital that object
               types have consistent meaning across all machines.

          Access:
               One of read-only, read-write, write-only, or
               not-accessible.

          Status:
              One of mandatory, optional, or obsolete.

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5.  Object Definitions

               RFC1156-MIB

               DEFINITIONS ::= BEGIN

               IMPORTS
                       mgmt, OBJECT-TYPE, NetworkAddress, IpAddress,
                       Counter, Gauge, TimeTicks
                           FROM RFC1155-SMI;

               mib        OBJECT IDENTIFIER ::= { mgmt 1 }

               system     OBJECT IDENTIFIER ::= { mib 1 }
               interfaces OBJECT IDENTIFIER ::= { mib 2 }
               at         OBJECT IDENTIFIER ::= { mib 3 }
               ip         OBJECT IDENTIFIER ::= { mib 4 }
               icmp       OBJECT IDENTIFIER ::= { mib 5 }
               tcp        OBJECT IDENTIFIER ::= { mib 6 }
               udp        OBJECT IDENTIFIER ::= { mib 7 }
               egp        OBJECT IDENTIFIER ::= { mib 8 }

               END

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5.1.  The System Group

          Implementation of the System group is mandatory for all
          systems.

          OBJECT:
          -------
               sysDescr { system 1 }

          Syntax:
               OCTET STRING

          Definition:
               A textual description of the entity.  This value should
               include the full name and version identification of the
               system's hardware type, software operating-system, and
               networking software.  It is mandatory that this only
               contain printable ASCII characters.

          Access:
               read-only.

          Status:
               mandatory.


          OBJECT:
          -------
               sysObjectID { system 2 }

          Syntax:
               OBJECT IDENTIFIER

          Definition:
               The vendor's authoritative identification of the network
               management subsystem contained in the entity.  This value
               is allocated within the SMI enterprises subtree
               (1.3.6.1.4.1) and provides an easy and unambiguous means
               for determining "what kind of box" is being managed.  For
               example, if vendor "Flintstones, Inc." was assigned the
               subtree 1.3.6.1.4.1.42, it could assign the identifier
               1.3.6.1.4.1.42.1.1 to its "Fred Router".

          Access:
               read-only.

          Status:
               mandatory.

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          OBJECT:
          -------
               sysUpTime { system 3 }

          Syntax:
               TimeTicks

          Definition:
               The time (in hundredths of a second) since the network
               management portion of the system was last re-initialized.

          Access:
               read-only.

          Status:
               mandatory.

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5.2.  The Interfaces Group

          Implementation of the Interfaces group is mandatory for all
          systems.

          OBJECT:
          -------
               ifNumber { interfaces 1 }

          Syntax:
               INTEGER

          Definition:
               The number of network interfaces (regardless of their
               current state) on which this system can send/receive IP
               datagrams.

          Access:
               read-only.

          Status:
               mandatory.

5.2.1.  The Interfaces Table

          OBJECT:
          -------
               ifTable { interfaces 2 }

          Syntax:
               SEQUENCE OF IfEntry

          Definition:
               A list of interface entries.  The number of entries is
               given by the value of ifNumber.

          Access:
               read-write.

          Status:
               mandatory.

          OBJECT:
          -------
               ifEntry { ifTable 1 }

          Syntax:
               IfEntry ::= SEQUENCE {

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                    ifIndex
                        INTEGER,
                    ifDescr
                        OCTET STRING,
                    ifType
                        INTEGER,
                    ifMtu
                        INTEGER,
                    ifSpeed
                        Gauge,
                    ifPhysAddress
                        OCTET STRING,
                    ifAdminStatus
                        INTEGER,
                    ifOperStatus
                        INTEGER,
                    ifLastChange
                        TimeTicks,
                    ifInOctets
                        Counter,
                    ifInUcastPkts
                        Counter,
                    ifInNUcastPkts
                        Counter,
                    ifInDiscards
                        Counter,
                    ifInErrors
                        Counter,
                    ifInUnknownProtos
                        Counter,
                    ifOutOctets
                        Counter,
                    ifOutUcastPkts
                        Counter,
                    ifOutNUcastPkts
                        Counter,
                    ifOutDiscards
                        Counter,
                    ifOutErrors
                        Counter,
                    ifOutQLen
                        Gauge
               }

          Definition:
               An interface entry containing objects at the subnetwork
               layer and below for a particular interface.

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          Access:
               read-write.

          Status:
               mandatory.


          We now consider the individual components of each interface
          entry:


          OBJECT:
          -------
               ifIndex { ifEntry 1 }

          Syntax:
               INTEGER

          Definition:
               A unique value for each interface.  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.

          Access:
               read-only.

          Status:
               mandatory.


          OBJECT:
          -------
               ifDescr { ifEntry 2 }

          Syntax:
               OCTET STRING

          Definition:
               A text string containing information about the interface.
               This string should include the name of the manufacturer,
               the product name and the version of the hardware
               interface.  The string is intended for presentation to a
               human; it must not contain anything but printable ASCII
               characters.

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          Access:
               read-only.

          Status:
               mandatory.


          OBJECT:
          -------
               ifType { ifEntry 3 }

          Syntax:
               INTEGER {
                    other(1),          -- none of the following
                    regular1822(2),
                    hdh1822(3),
                    ddn-x25(4),
                    rfc877-x25(5),
                    ethernet-csmacd(6),
                    iso88023-csmacd(7),
                    iso88024-tokenBus(8),
                    iso88025-tokenRing(9),
                    iso88026-man(10),
                    starLan(11),
                    proteon-10MBit(12),
                    proteon-80MBit(13),
                    hyperchannel(14),
                    fddi(15),
                    lapb(16),
                    sdlc(17),
                    t1-carrier(18),
                    cept(19),          -- european equivalent of T-1
                    basicIsdn(20),
                    primaryIsdn(21),
                                        -- proprietary serial
                    propPointToPointSerial(22)
               }

          Definition:
               The type of interface, distinguished according to the
               physical/link/network protocol(s) immediately "below" IP
               in the protocol stack.

          Access:
               read-only.

          Status:
               mandatory.

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          OBJECT:
          -------
               ifMtu { ifEntry 4 }

          Syntax:
               INTEGER

          Definition:
               The size of the largest IP datagram which can be
               sent/received on the interface, specified in octets.

          Access:
               read-only.

          Status:
               mandatory.


          OBJECT:
          -------
               ifSpeed { ifEntry 5 }

          Syntax:
               Gauge

          Definition:
               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.

          Access:
               read-only.

          Status:
               mandatory.


          OBJECT:
          -------
               ifPhysAddress { ifEntry 6 }

          Syntax:
               OCTET STRING

          Definition:
               The interface's address at the protocol layer immediately

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               "below" IP in the protocol stack.  For interfaces which
               do not have such an address (e.g., a serial line), this
               object should contain an octet string of zero length.

          Access:
               read-only.

          Status:
               mandatory.


          OBJECT:
          -------
               ifAdminStatus { ifEntry 7 }

          Syntax:
               INTEGER {
                    up(1),       -- ready to pass packets
                    down(2),
                    testing(3)   -- in some test mode
                  }

           Definition:
               The desired state of the interface.  The testing(3) state
               indicates that no operational packets can be passed.

           Access:
               read-write.

           Status:
               mandatory.


          OBJECT:
          -------
               ifOperStatus { ifEntry 8 }

          Syntax:
               INTEGER {
                    up(1),       -- ready to pass packets
                    down(2),
                    testing(3)   -- in some test mode
               }

          Definition:
               The current operational state of the interface.  The
               testing(3) state indicates that no operational packets
               can be passed.

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          Access:
               read-only.

          Status:
               mandatory.


          OBJECT:
          -------
               ifLastChange { ifEntry 9 }

          Syntax:
               TimeTicks

          Definition:
               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.

          Access:
               read-only.

          Status:
               mandatory.


          OBJECT:
          -------
               ifInOctets { ifEntry 10 }

          Syntax:
               Counter

          Definition:
               The total number of octets received on the interface,
               including framing characters.

          Access:
               read-only.

          Status:
               mandatory.

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          OBJECT:
          -------
               ifInUcastPkts  { ifEntry 11 }

          Syntax:
               Counter

          Definition:
               The number of (subnet) unicast packets delivered to a
               higher-layer protocol.

          Access:
               read-only.

          Status:
               mandatory.


          OBJECT:
          -------
               ifInNUcastPkts { ifEntry 12 }

          Syntax:
               Counter

          Definition:
               The number of non-unicast (i.e., subnet broadcast or
               subnet multicast) packets delivered to a higher-layer
               protocol.

          Access:
               read-only.

          Status:
               mandatory.


          OBJECT:
          -------
               ifInDiscards { ifEntry 13 }

          Syntax:
               Counter

          Definition:
               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

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               protocol.  One possible reason for discarding such a
               packet could be to free up buffer space.

          Access:
               read-only.

          Status:
               mandatory.


          OBJECT:
          -------
               ifInErrors { ifEntry 14 }

          Syntax:
               Counter

          Definition:
               The number of inbound packets that contained errors
               preventing them from being deliverable to a higher-layer
               protocol.

          Access:
               read-only.

          Status:
               mandatory.


          OBJECT:
          -------
               ifInUnknownProtos { ifEntry 15 }

          Syntax:
               Counter

          Definition:
               The number of packets received via the interface which
               were discarded because of an unknown or unsupported
               protocol.

          Access:
               read-only.

          Status:
              mandatory.

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          OBJECT:
          -------
               ifOutOctets { ifEntry 16 }

          Syntax:
               Counter

          Definition:
               The total number of octets transmitted out of the
               interface, including framing characters.

          Access:
               read-only.

          Status:
               mandatory.


          OBJECT:
          -------
               ifOutUcastPkts { ifEntry 17 }

           Syntax:
               Counter

          Definition:
               The total number of packets that higher-level protocols
               requested be transmitted to a subnet-unicast address,
               including those that were discarded or not sent.

          Access:
               read-only.

          Status:
               mandatory.


          OBJECT:
          -------
              ifOutNUcastPkts { ifEntry 18 }

          Syntax:
               Counter

          Definition:
               The total number of packets that higher-level protocols
               requested be transmitted to a non-unicast (i.e., a subnet
               broadcast or subnet multicast) address, including those

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               that were discarded or not sent.

          Access:
               read-only.

          Status:
               mandatory.


          OBJECT:
          -------
               ifOutDiscards { ifEntry 19 }

          Syntax:
               Counter

          Definition:
               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.

          Access:
               read-only.

          Status:
               mandatory.


          OBJECT:
          -------
               ifOutErrors { ifEntry 20 }

          Syntax:
               Counter

          Definition:
               The number of outbound packets that could not be
               transmitted because of errors.

          Access:
               read-only.

          Status:
               mandatory.

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          OBJECT:
          -------
               ifOutQLen { ifEntry 21 }

          Syntax:
               Gauge

          Definition:
               The length of the output packet queue (in packets).

          Access:
               read-only.

          Status:
               mandatory.

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5.3.  The Address Translation Group

   Implementation of the Address Translation group is mandatory
   for all systems.

   The Address Translation group contains one table which is the
   union across all interfaces of the translation tables for
   converting a NetworkAddress (e.g., an IP address) into a
   subnetwork-specific address.  For lack of a better term, this
   document refers to such a subnetwork-specific address as a
   "physical" address.

   Examples of such translation tables are:  for broadcast media
   where ARP is in use, the translation table is equivalent to
   the ARP cache; or, on an X.25 network where non-algorithmic
   translation to X.121 addresses is required, the translation
   table contains the NetworkAddress to X.121 address
   equivalences.

          OBJECT:
          -------
               atTable { at 1 }

          Syntax:
               SEQUENCE OF AtEntry

          Definition:
               The Address Translation tables contain the NetworkAddress
               to "physical" address equivalences.  Some interfaces do
               not use translation tables for determining address
               equivalences (e.g., DDN-X.25 has an algorithmic method);
               if all interfaces are of this type, then the Address
               Translation table is empty, i.e., has zero entries.

          Access:
               read-write.

          Status:
               mandatory.


          OBJECT:
          -------
               atEntry { atTable 1 }

          Syntax:
               AtEntry ::= SEQUENCE {
                    atIfIndex

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                        INTEGER,
                    atPhysAddress
                        OCTET STRING,
                    atNetAddress
                        NetworkAddress
               }

          Definition:
               Each entry contains one NetworkAddress to "physical"
               address equivalence.

          Access:
               read-write.

          Status:
               mandatory.

          We now consider the individual components of each Address
          Translation table entry:


          OBJECT:
          -------
               atIfIndex { atEntry 1 }

          Syntax:
               INTEGER

          Definition:
               The interface on which this entry's equivalence is
               effective.  The interface identified by a particular
               value of this index is the same interface as identified
                by the same value of ifIndex.

          Access:
               read-write.

          Status:
               mandatory.


          OBJECT:
          -------
               atPhysAddress { atEntry 2 }

          Syntax:
               OCTET STRING

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          Definition:
               The media-dependent "physical" address.

          Access:
               read-write.

          Status:
               mandatory.


          OBJECT:
          -------
               atNetAddress { atEntry 3 }

          Syntax:
               NetworkAddress

          Definition:
               The NetworkAddress (e.g., the IP address) corresponding to
               the media-dependent "physical" address.

          Access:
               read-write.

          Status:
               mandatory.


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