We have an ongoing issue with our 2930 frequently (every few days) dropping almost all its VPN connections and the only fix is a reboot. Having finally caught the issue as soon as it happens, the syslog entries show a whole slew of these:

Vigor: ARP address mismatch - Ethernet source address doesn't match ARP sender address 192.168.200.1

Anyone seen this before for a specific reason or could the router somehow be corrupting its ARP table?