I use cisco 2811 router when I try to config s0/0/0 serial interface using
(config)#int serial 0/0/0commond it says "%Invalid interface type and number" what's wrong with this commond?
The router does not think it has an interface with that name run show ip int brief to get a list of interfaces present in the router
This may be of help.
Interface and Line Numbers in Cisco 1800, 2800 and 3800 Series Routers