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Failing link, debug serial int errors

Hi ,

I have a ppp 64k leased line with a Cisco 2600 sat at either side running at 64k. They have been working well for a long time but have recently failed to pass traffic. The telco has confirmed the links are good (usually the problem!) to the ntu's so I am trying to troubleshoot the routers.

I am running debug serial interfaces on either side am getting 2 sets of very different results. Can anyone suggest where I should start or what these debugs mean ?

I have also attached a copy of sh int s0/0 from one end. Both ends read very much the same.

Notes :

1. I have tried a shut and a full reboot at both sides but this has not worked.

2. There have been no recent config changes on either router.

Do I have faulty kit ? if so which end ?

Any ideas greatly appreciated,



Re: Failing link, debug serial int errors


As per the attachment the serial link is showing down,also the crc,input errors are too much that too within 2hrs.

Better would suggst to get the physical loop up from telco and check the link for errors in looped condition.

also do keyin more about the remote serial interface o/p as well..

if possible do post out the config of the remote end serial interface coz its showing only dialer output in the debug..


Re: Failing link, debug serial int errors


Looks like homework for you to be done at Telco side.The numbers of CRC/ errors are related to Telco.Also the reliability should be 1/255(128/255 in your case).

Though we cannot discard the possibility of faulty equipment.

Your first move should be connecting the routers back-to-back with a DTE-DCE cable.

If the modems are supplied by Telco, then no issues, but if they are yours, check them also.

If no problems are found,then its definately telco's prob.

Try eliminating step-by-step by looping the modems etc.

Pls revert back if any probs.



VIP Purple

Re: Failing link, debug serial int errors


in addition to the other posts, there is a fairly comprehensive document (see the link below) that deals with all aspects of serial line troubleshooting, might be worth checking as well:

Troubleshooting Serial Lines