Serial Up, Line Prot Down

[AJ1982]

Dear All,

My wonderful Cisco lab has been having the rare habbit of a serial line suddnly going line protocol down. Yet the physical link stays.

Normally a power cycle works, however the test environment is used for project work and if went down in my absence, could not be restored.

This seems to have had a spate since a recent power outage, but I cant prove it.

The connections are serial to serial, router to router (DCE,DTE) so I am clocking on one end, that is all.

Are there any things im missing, or should I be looking for a hardware error, but then again wouldnt that affect the physical link, as opposed to the line protocol.

Thanks for any info.

AJ


===

Fatman Superstar (Andrew James)

CCNA,
(CCNA Cisco Academy Instructor Trained)

 

[syndicate47]

I'm not the worlds best Cisco person but I resently set up the same sort of test lab. Are you clocking the DCE end?

 

[geirendre]

What kind of encapsulation do you have on the link?
Do a "show interface s0" on both ends and compare.
They should be the same in both ends...
The router can see if it's the DCE or DTE side
of the cabel connected to a serial interface.
You get an error message if you try to set
clock rate on a DTE.

 

[Seanyfella]

I would agree that the issue is related to a configuration mis-match. As suggested earlier, check the config at each end. If they match up (encapsulation/speed/etc.), then try running a debug on the interfaces - that may highlight the reason for the problem.

Incidentally, did you check the router log file after the line went down (sh log)? If this doesn't provide enough info, try increasing the level of logging so that next time you will have a useful log file to start trouble-shooting with...