NerveCenter^TM 3.8: Node Classification - Contents - How NerveCenter Classifies a Node -
The Need for Node Classification      Classifying Nodes Manually

How NerveCenter Classifies a Node

NerveCenter tries to classify a node based on the highest version of SNMP implemented on the corresponding SNMP agent. You can, however, limit the highest version NerveCenter attempts to classify by specifying a maximum classification version in the NerveCenter Administrator. When you specify a maximum classification version, NerveCenter never attempts to classify a node above the version you specified.

When classifying a node, you need to know whether a particular version is supported on the corresponding agent, NerveCenter sends an SNMP GetRequest message and listens for the response. Receipt of an SNMP response or SNMP error indicates that the particular version is supported on the corresponding agent. If NerveCenter receives a response other than an SNMP reply, NerveCenter concludes that the particular version is not supported on the agent. To ascertain support for SNMP v1 and SNMP v2c, NerveCenter sends a GetRequest message for SysObjectID with a read community of public.

To ascertain SNMP v3 agents, NerveCenter sends the GetRequest message to discover the snmpEngineID at the agent on behalf of the `initial' user, as specified in the suggested engine discovery mechanism in RFC 2574.

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   Whenever NerveCenter ascertains that an agent supports SNMP v3, NerveCenter also assigns a default security level for communication with the node as NoAuthNoPriv. Please refer to NerveCenter online help for details about changing a node's default security level or configuring an initial user on SNMP v3 agents.

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Irrespective of the SNMP version of the node, NerveCenter always tries to ascertain the node's SNMP version with the "Maximum Classification Version" specified.

If NerveCenter does not get SNMP responses or SNMP errors to its GetRequest messages, then NerveCenter designates such nodes as `unknown'. For details of the algorithm NerveCenter uses to classify nodes, see Node Classification Algorithm.

The you can also test a particular version specified on a node. In the NerveCenter Client, select the node from the node list view and selecting Test Version from the right mouse click menu. This Test Version is similar to the GetRequest discussed above. If the agent does not support the version specified on the node, you get a test version failed error message.

Specifying a Maximum Classification Version

You can specify the maximum classification version as the highest SNMP version up to which you want NerveCenter to classify a node. NerveCenter will never attempt to classify a node for any version above the version you specify here. For example, if you select v2, NerveCenter never tries to classify the node above SNMP v2c; that is, NerveCenter will never send SNMP v3 requests to any nodes.

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   If you want NerveCenter to detect whether SNMP v3 is supported at an agent, the agent must have an initial user configured for discovery. Please refer to the Agent Setup section in NerveCenter online help to know how to configure agents for discovery.

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  To set the maximum classification version:

1. Open NerveCenter Administrator.
2. Connect to the NerveCenter Server.
3. Select the Classify tab.
4. Select the highest level you want to classify from the Maximum Version drop-down list box.
5. Select the Save button.