Most network equipment has the abitlty to enable snmp on the device. Once you do that, you will then use the nagios check_snmp plugins to query the device for status of many items. To find out what you have available to query, you might just need a MIB for that device. See the dealer for this file, or a google search. If you don't have a MIB browser, get one. Mbrowse is nice for linux, and there are many for winblows. Now that you have a MIB browser, you can just browse through the MIB, looking at all the stuff you can get from the device, and try each one out right in the mib browser, before you even try the nagios plugin. Now that you know what you are going to check, setup your check_snmp checks appropriately and for God's sake, use -m with the check_snmp to tell the plugin to use MIBwhatever.
BTW, many devices come with there very own utilities. Most of the time, anything that can be read/configured/etc from these utilities via telnet or however, can be done using snmp.
For example on a switch, we can telnet to the device and look at the spanning tree status of a port, or we could use check_snmp check to do the same thing.
Edited Fri Dec 16 2005, 03:41PM ]