Weird IP/routing issue - any ideas?
Got a weird one here that has been driving me crazy this week. Open to any and all suggestions.
Got a customer with a very simple network setup:
Cisco router
|
Cisco 1900 series switch
|..........|..........|
box1....box2....box3
Both boxes are running Linux. The problem is an IP that's bound to the interface on box1 keeps disappearing to the outside world. Eventually discovered the ARP table on the router thinks that IP should be routed to the interface on box2. I've been monitoring both boxes and am confident that the IP has never actually been bound to the interface on box2. It first happened Saturday, then Tuesday, then 4 times on Thursday. No hardware or configuration changes have been made to this network in months.
When this happens, no one beyond the router can reach the IP because the router thinks it should be going to box2, per its ARP table. The funny thing is, we can login to box2 or box3 and connect to the IP on box1 without a problem.
The temp fix has been to add a static entry in the router's table to direct that IP to the box1 MAC address. This is only a band-aid though, what could be going on here?
Some have suggested that the Cisco 1924, being rather old, could have a hardware issue that was corrupting its mac-address-table or similar, but since it's a L2 device it's hard to get much meaning information out of it.
Any guesses appreciated!
Brandon
