Specifications

Watson Ethernet

Operating Manual

Watson-Ethernet-Manual.doc

Version 3.3-01

8-2

Revision: 2010-01-20

Subrack-wide information (e.g. inventory of subrack slots and the plug-ins con-

tained in the slots) is handled by a rack agent. This rack agent is a subagent re-

siding on the same plug-in as the master agent.

ENTITIY-MIB

ifTable

Figure 8-1: SNMP Master agent and subagents

8.1.2 Default Context and Card Contexts

AgentX is optimized to access tabular information distributed over several sub-

agents. Each subagent handles certain rows of one or more tables containing

management information. For instance the subagent on a plug-in is responsible

for the rows in the ifTable representing the interfaces physically contained on

this plug-in.

Some data structures cannot reasonably be distributed over several subagents

with the AgentX protocol. An example is the scalars and tables used to manage

the Rapid Spanning Tree protocol: on each plug-in we need an own set of sca-

lars/tables representing timers, priorities, port states etc.

To access these per-card data structures we use "Card Contexts" which are

SNMP community strings specific for each plug-in in a subrack.

Card Contexts are formed by appending the characters @slotnn to the "Default

Context":

 The Default Context is the SNMP community string. It consists of the two

strings defined with the Monitor commands SNMPCOMMUNITY READ and

SNMPCOMMUNITY WRITE.

 nn is the number of the subrack slot (1 .. 12)

 If the plug-in is inserted in the minirack mechanics or in the tabletop housing

for plug-ins then the Card Context is community@slot1