The problem is that one of the servers outside the PIX with a default route to the 2600 interface will communicate with the interface of the 2600 and beyond for about one hour and then it will be unable to communicate after that. It can, however, still communicate with everything behind the PIX interface. If the ARP cache is flushed for the CISCO 2600 then the communication starts again for about one hour before it drops. If we move the problem server to a different subnet in the WAN that is on another interface in the Cisco 2600 the problem disappears. Do you think the problem could be caused by the PIX or a server behind the firewall? We have already done all the standard trouble-shooting. (i.e. replacing patch cables, NIC, router, switch, etc.)
Have you tried changing the interface card on the router? Try tweaking input and output queues on this interface.
This was first published in December 2003