We're running multiple leased-line DS-3s in our backbone. Recently I've spent several weeks troubleshooting one DS-3 going down for an hour or so every few weeks. CRCs on both ends. The long haul carrier saw frequency errors of -88ppm (20ppm is acceptable). There are multiple carriers in this link, as well as our other DS-3s.
Card swaps did not alleviate the errors (no h/w problem).
Carriers are all running Strata 3 clocks. Carrier and I agreed to change from 'clock source line' to 'clock source internal' on one router. Problem solved.
Carrier mentioned to me they see this more and more and attribute it to the many new carriers and errors in Strata 3 synchronization among them.
I'm considering changing all backbone DS-3s to internal but am interested if anyone else is seeing this problem before I re-provision these links.
The focus of this board is Virtual Private Networks, however, there are a number of professionals online who may be able to assist you. We are always considering additional forums for such topics and I will make a note of your post.
If you don't get a suitable response to your post, you may wish to review our resources at the online Technical Assistance Center (www.cisco.com/tac) or speak with a TAC engineer. You can open a TAC case online at www.cisco.com/tac/caseopen
If anyone else in the forum has some advice, please reply to this thread.
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