Essential SNMP

External Polling

It is often impossible to poll a device internally, for technical, security, or political reasons. For example, the System Administration group may not be in the habit of giving out the root password, making it difficult for you to install and maintain internal polling scripts. However, they may have no problem with installing and maintaining an SNMP agent such as Concord’s SystemEDGE or Net-SNMP. It’s also possible that you will find yourself in an environment in which you lack the knowledge to build the tools necessary to poll internally. Despite the situation, if an SNMP agent is present on a machine that has objects worth polling, you can use an external device to poll the machine and read the objects’ values.^[36] This external device can be one or more NMSs or other machines or devices. For instance, when you have a decent-sized network it is sometimes convenient, and possibly necessary, to distribute polling among several NMSs.

Each of the external polling engines we will look at uses the same polling methods, although some NMSs implement external polling differently. We’ll start with the OpenView xnmgraph program, which can be used to collect and display data graphically. You can even use OpenView to save the data for later retrieval and analysis. We’ll include some examples that show how you can collect data and store it automatically and how you can retrieve that data for display. Castle Rock’s SNMPc also has an excellent data-collection facility ...