I have a Cisco 2801 ISR with IOS 12.4. It has a basic configuration with F0/0 connected to the public internet and F0/1 connected to my private LAN. My problem is when I administratively shutdown of F0/0, for testing purposes, my connectivity to the LAN interface, is lost. Interestingly however, when I connect to the router via console cable; F0/1 shows as being up and line protocol up and it can be pinged locally however from the router I cannot ping into the rest of the LAN. Executing the clear interface F0/1 command fixes the problem however I don't believe this behaviour is normal. When F0/0 is brought back online, all connectivity is restored. Please let me know if you require any further details or configuration commands, any help would be greatly appreciated.
Thanks in advance,