We're running several Windows 2003 servers behind an ASA5520. Every so often, one of the Windows boxes will become inaccessible from outside the firewall but the other boxes behind the firewall can still see it and communicate with it. Right clicking the network adapter and clicking "Repair" on the affected server fixes the problem for a few days. A colleague suggested this might be cause by a a stale ARP cache on the ASA. Does that seem correct? And if it is, how can we make sure it doesn't happen again?