I have one of the strangest networking problems I have seen in my 20+ years of working with computers. Beginning last Thursday night, every 4 hours (give or take about 15 minutes) my primary server looses communication with the internet. When this happens, people on the outside can't even get a ping response from the server.
The server is running Server 2003.
The router is an old Cisco 2611 that has been in service for us for about 6 months.
The router has a single host connection pointing to the server's IP address (10.6.6.1)
Here are some of the behaviors that I have noted:
The server is accessible by everything on the LAN and vice versa.
The server can ping the router.
The server can NOT ping anything beyond the router.
The router can ping anything on the WAN and on the LAN, including the server.
The router can be reached from the WAN via its own IP address.
If I clear the arp cache on the router, then after about 30-60 seconds everything returns to normal for the next four hours.
Here are just a few of the many steps I have taken to try to solve the problem:
Changed the arp timeout from the default 4 hours to 30 minutes
Physically removed the server from the LAN and put another server in its place, using the original server's IP address. (It still failed after 4 hours.)
Setup a syslog server and set it to "logging history warnings" but it is not giving me any errors.
The server is connected to a switch before it gets to the router, but directly plugging the server into the router did not stop the problem.
Unless someone can help me figure this out, the only options I see that I am left with are replacing the router or setting up the server to act as the router with RRAS.
Thanks in advance for any help you can give me.