Routing table problems include but are not limited to:
inactive routes
unnecessary routes
black hole routes
flapping links (links that go up and come down) that cause the routes to flap
incorrect route tables
invalid Address Resolution Protocol (ARP) cache that causes incorrect IP to MAC assignment
problems with administrative distance or other parameters
Important
Do not restart a device to clear a problem. In restarting the device, you also clear the logs. Logs are vital and can help determine many problems.