RFC 2037 (rfc2037) - Page 3 of 35
Entity MIB using SMIv2
Alternative Format: Original Text Document
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