Using Multiple SNMP Agents

This section discusses the following topics:

• SNMP Agent as Proxy for Other Agents

• Configuring an SNMP Proxy

The original SNMP management model allowed for only a single, monolithic agent to carry out all management responsibilities on a given network node (IP address). This solution was not flexible enough to provide for effective management of increasingly complex systems. In addition to the agents typically provided by computer manufacturers for hardware and operating system information, agents are also produced by vendors of other products, such as agents for SQL database systems. Complex and heterogeneous systems thus require the ability to accommodate multiple agents on a single network node.

 

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SNMP Agent as Proxy for Other Agents

This weakness of the original SNMP model led to the concept of an SNMP master agent that acts as a proxy for other SNMP agents. The WebLogic SNMP agent can function as a master agent in this sense. To use the master agent functionality of the WebLogic SNMP agent, you can assign branches of the registration tree (OID tree) as the responsibility of other SNMP agents. Each of these will be a branch that encompasses the private MIB (or some part of that MIB) which the target agent is designed to manage.

Note: You cannot use the WebLogic SNMP agent as a proxy for SNMP agents in other WebLogic Server domains. For example, WebLogic domainA's SNMP agent cannot proxy requests to domainB's SNMP agent. This limitation is in effect because all WebLogic SNMP agents use the same MIB root.

Instead of proxying requests to multiple WebLogic Server domains, you can place all of your server instances in a single domain and send requests directly to each Managed Server. See Using Community Names to Specify Target Servers in Management Requests.

The WebLogic SNMP agent listens for requests from SNMP managers and then fans out these requests to other SNMP agents on the Administration Server machine, if the attribute requested has an OID falling under the branch of the OID tree assigned to one of those other agents. By default the WebLogic SNMP agent listens for management requests on port 161. If the WebLogic SNMP agent is to proxy for other SNMP agents, then those other agents must be configured to listen for SNMP management requests on a port other than the port that the WebLogic SNMP agent is using to receive requests from SNMP managers.

The Microsoft Windows SNMP Service

While the WebLogic Server SNMP agent can be a proxy for other SNMP agents, it cannot be configured as a subagent of the Microsoft Windows SNMP agent service.

Using Microsoft Extension Agent API, the Microsoft Windows 2000 SNMP agent service can be a proxy for other SNMP agents. However, WebLogic Server does not support this feature and cannot use the Windows SNMP agent as a proxy.

 

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Configuring an SNMP Proxy

To configure the WebLogic SNMP agent to proxy for another SNMP agent, do the following:

1. Invoke the Administration Console (if it isn't running already).

2. Select SNMP—>SNMP Proxies in the left pane. This invokes the SNMP Proxies table, which lists entries for all the SNMP agents you have configured the WebLogic SNMP agent to proxy for.

3. To create a new proxy, select the Create a new SNMP Proxy link to invoke the SNMP Proxy configuration screen. Fill out the fields on this screen as follows:

   • Name — Enter a name for the proxy in this field. This should be descriptive of the agent that the requests will be forwarded to, such as "OracleDBAgent."

   • Port — Enter a port number for communication with the other SNMP agent. The agent being proxied for must be configured to expect SNMP management requests on this port number. This must be a port number other than the port being used by the WebLogic SNMP agent for communication with SNMP managers.

   • OID Root — This is an absolute OID that designates the root, or top node, of the part of the OID tree being assigned to that agent.

   • Community — This is the community name that the other agent expects in requests from SNMP managers.

   • Timeout — This is the interval, in seconds, that the WebLogic SNMP proxy agent waits for a response to requests forwarded to another SNMP agent. If this interval elapses without a response from the other agent, the WebLogic SNMP agent will send an appropriate error to the requesting manager.

4. Click Apply to create the new proxy.

5. Restart the Administration Server so that your changes can take effect.