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Clocking Issues

Hello Everyone,

Wondering if anyone else has ran into this before. I have a 2821 router with (3) VWIC2-2MFT-T1/E1 cards. I have (2) data T1s on card 0 and (3) PRIs spread accross cards 1 and 2. The two data T1s are bonded into a multilink interface and are both from the same provider. All interfaces are set to 'clock source line' and my network clocking looks like this:

network-clock-participate wic 0
network-clock-participate wic 1
network-clock-participate wic 2
network-clock-select 1 T1 0/1/0
network-clock-select 2 T1 0/2/0

So my problem is that the data T1s are taking many input and CRC errors whilst the controllers are taking many slips. Of course, I believe this is a clocking problem. My PRIs are running clean. So to put the two data T1s on their own clocking domain, I enter the command:

no network-clock-participate wic 0

This causes the WAN connection to go down. If I put 'network-clock-participate wic 0' back in the WAN still stays down. I have to reload the router to get it back up. It's a remote site so I can't do much troubleshooting while it's down. I had a user at that site run a few commands for me and I see that while the WAN is down, both controllers are up and both serial interfaces are up/down.

I have at least 20 other remote sites that I'm able to have this sort of configuration at so I'm wondering what the problem may be. I don't think it seems like a hardware issue, but it may be. I have been working with TAC for the past week but they've been of little help so far.

Thanks for any input,


Cisco Employee

Re: Clocking Issues

One question -  Are the data T1s "real" T1s, or emulated T1s, like CEoIP?  I have seen cases where emulated T1s are actually expecting clocking from the router (clock source internal) since they act (effectively) as termination points.

What does your carrier recommend in terms of clocking?

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