In case someone else finds this useful here is a Perl program to report on the devices attached to network switches. It was derived from Tobias Oetiker's cammer and has added further information about each device.
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To use it you need to know SNMP read-permission community strings for your routers and switches.
A couple of years ago the program was used extensively to gather information on devices connected to a Cisco network so I'm including a Cisco group in the distribution. I'm not in a position to do further work on the program at present but as long as the interface to the SNMP support libraries has not changed it should still work just as it did before.
The web page explains what it does and gives full details on how to set it up.
James