There is likely nothing random about it. Accessing forwarding tables on Cisco devices is quite awkward, since Cisco ignores the Q-BRIDGE-MIB - which may be related to your issue (but I suppose you are accounting for community indexing when snmpwalking?).
Yes. The mac addresses are there.
I'd suggest addding "nav.ipdevpoll.plugins.cam = DEBUG" to NAV's `logging.conf` and then restarting ipdevpoll to see what this plugin logs during the execution of topo jobs.
We've tried this, and nothing is logged other than "topo for <switch> completed in ..."
Should we try to activate the old topology detector (/usr/lib/nav/network-discovery)?
best regards Andreas Dobloug USIT/UiO