Solstice Enterprise Agents 1.0 User Guide

3.1 SNMP-Based Master/Subagent Overview

The Master Agent is the main component of Solstice Enterprise Agent technology. It runs as a daemon process and listens to User Datagram Protocol (UDP) port 161 for SNMP requests. The Master Agent also opens another port to receive SNMP trap notifications from various subagents. These traps are forwarded to various managers, as determined by the configuration files.

3.1.1 Invoking the Master Agent

A system startup script file invokes the Master Agent when the system is initially booted. Upon the Master Agent's invocation, it reads its various configuration files and appropriate actions are performed by activating subagents, determining the subtree OID for various subagents, populating its own MIBs. The Master Agent provides the following functionality:

Note -

If you have snmpd (part of Domain Manager) or some other SNMP agent using port 161 running, the Solstice Enterprise Agents cannot run.

3.1.2 Invoking the Subagent

A subagent can be invoked in the following ways:

3.1.3 Communicating With the Subagent

Any communication from subagents to the Master Agent is done through UDP port 161. The topic of sending traps to the Master Agent from the subagents is discussed in "3.1.6 Trap Notification".

Note -

The Master Agent communicates on separate ports for each subagent.

The Master Agent also checks to be sure that registered subagents are up and running, based on the following conditions:

3.1.4 Registering the Subagent

To register the subagent, the Master Agent binds it to the MIB. The Master Agent then determines its present location, using one of the following methods:

The binding policy relates to the registration of SNMP object identifiers (OIDs). It involves decision-making on the part of the Master Agent when dispatching SNMP requests to various subagents. The Master Agent supports the binding policy, as shown in Table 3-1.

Table 3-1 Binding Policy

Type of Registration 

Method of Registration 

Individual variable registration 

A subagent can manage individual variables 

Row registration 

A subagent can manage each row or multiple rows 

Table registration 

A subagent can register full and partial tables; partial table registration means that some columns of a table can be registered; for example, if a table has columns c1-c5, a subagent can then register a partial table managing c3 and c5 columns (only) of that table 

Duplicate registration 

NOT allowed 

Overlapping registration 

In the case of overlapped registration, the Master Agent dispatches requests on the basis of best OID match 

3.1.5 Sending Requests

The Master Agent supports the forwarding of SNMP requests (Get, Get Next, and Set) in two modes. The mode is indicated by providing an optional argument with the command-line invocation. These modes are:

Following is a list of allowable send requests.

3.1.6 Trap Notification

The subagents send the traps to the Master Agent; the Master Agent the decides which managers will receive the trap. This decision is configurable.