Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

Serial Interface high number of errors

6 input errors, 6 CRC, 1 frame, 0 overrun, 0 ignored, 0 abort

7346 packets output, 1637988 bytes, 0 underruns

0 output errors, 0 collisions, 181 interface resets, 0 restarts

0 output buffer failures, 0 output buffers swapped out

8 carrier transitions. How do I tell if this is a faulty eternal CSU/DSU or a Telco problem? Thanks in advance.

New Member

Re: Serial Interface high number of errors

There are a few ways to accomplish this. Here are two:

Plug a T1 loopback into the T1 port in question (this will interrupt connectivity) and send constant traffic to the IP address assigned to that port. See if the errors continue to increment.

Bridge the T1 through a T1 test set and see which direction you're getting the errors from (likely bursts of all ones pattern from one side).

Below is a good link on troubleshooting T1/E1 issues:

New Member

Re: Serial Interface high number of errors


You can also work with Telco to provide loops from their network and you can test from the A and Z ends of the ckt (provided you own the routers at each end). This will help to isolate which side you're seeing a problem with. Also you should verify the timing configuration with what you have configured and what the Telco is providing (e.g. internal or line).

You can put the CSU/DSU into a local (DTE) loopback and test from the router to the loop as well. Also, as previously mentioned use a loopback plug to put a hard loop up and test to it.

Hope this helps.



CreatePlease login to create content