RFC 2037 (rfc2037) - Page 3 of 35

Entity MIB using SMIv2

RFC 2037                 Entity MIB using SMIv2             October 1996


3.  Overview

   There is a need for a standardized way of representing a single agent
   which supports multiple instances of one MIB.  This is presently true
   for at least 3 standard MIBs, and is likely to become true for more
   and more MIBs as time passes.  For example:

      - multiple instances of a bridge supported within a single
        device having a single agent;

      - multiple repeaters supported by a single agent;

      - multiple OSPF backbone areas, each one operating as part
        of its own Autonomous System, and each identified by the
        same area-id (e.g., 0.0.0.0), supported inside a single
        router with one agent.

   The fact that it is a single agent in each of these cases implies
   there is some relationship which binds all of these entities
   together.  Effectively, there is some "overall" physical entity which
   houses the sum of the things managed by that one agent, i.e., there
   are multiple "logical" entities within a single physical entity.
   Sometimes, the overall physical entity contains multiple (smaller)
   physical entities and each logical entity is associated with a
   particular physical entity.  Sometimes, the overall physical entity
   is a "compound" of multiple physical entities (e.g., a stack of
   stackable hubs).

   What is needed is a way to determine exactly what logical entities
   are managed by the agent (either by SNMPv1 or SNMPv2), and thereby to
   be able to communicate with the agent about a particular logical
   entity.  When different logical entities are associated with
   different physical entities within the overall physical entity, it is
   also useful to be able to use this information to distinguish between
   logical entities.

   In these situations, there is no need for varbinds for multiple
   logical entities to be referenced in the same SNMP message (although
   that might be useful in the future).  Rather, it is sufficient, and
   in some situations preferable, to have the context/community in the
   message identify the logical entity to which the varbinds apply.










McCloghrie & Bierman        Standards Track