line protocol down

[dmalamba]

MY 2610 router had 5 serial line protocols down. My telcomms company has verified that all the lines are ok. One of the interfaces now is up. I dont know how I can debug the router to check what the problem may be. If I use the clear interface command for these interfaces, will I not lose my configuration on those interfaces. I tried to use the no shutdown command but doesnt help. Help please.

[pelford]

Line protocol down means that the router cannot see "keepalive" packets from a router at the other end of the serial link. This might be because the encapsulation configured on the routers at each end of the serial link is different, eg. one end "encapsulation hdlc" (the default) and the other end "encapsulation ppp". You can check this using "show interface". You should also use the output of this command to check when thge the "last input" and "last output" of traffic occurred. Additional analysis can be done using the "debug serial packet" and "debug serial interface" commands