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New Member

Multiple T1s in data bundle and Clocking Domain

Scenario: 2851 ISR with 2 VWIC-2MFT-T1 installed, one in WIC Slot 1 and the other in WIC Slot 2. Controller T1 0/1/0 is a PRI Voice only, 0/1/1 is DS0 CAS. ?network-clock-participate wic 1? and select 0/1/0 first the 0/1/1 second. This is so they can use the DSP resources on the router system board PVDM Slot(s) in this case. I understand relationship between voice T1s and the clocking domain. My question or discussion is when you have a MLPPP bundle on the VWIC-2MFT-T1 in WIC Slot 2, I would have it NOT participate in any ?clocking domain? (ANY TAKERS?) Then, to extend the question a bit more; of the 2 T1s in the bundle one should ?clock source line? and the other internal?

Hall of Fame Super Gold

Re: Multiple T1s in data bundle and Clocking Domain


use source line all times you are connected to telco circuits, mlppp or not.

Set network-clock-select among them as you wish.

The CAS T1 that is likely going to a PBX should have clock internal and the PBX to take clock from it.

hope this helps, please rate post if it does!

New Member

Re: Multiple T1s in data bundle and Clocking Domain

As a rule of thumb I agree but in this case the PBX if supplying clock. I know usually each T1 data would be configured to take clock off of line but with bundlesMLF, MLPPP, etc. the providers are not all doing it that way. We several customers that we HAD to configure one and only one of the T1s as line and others in the same bundle as internal.

Cisco Employee

Re: Multiple T1s in data bundle and Clocking Domain

commenting on an old post...

Is there a best practice to follow here regarding clock source on multiple T1's in a bundle? Based on the last comment, it sounds like each case depends on the carrier configuration, but I want to make sure I understand. Right now I'm running an 8xT1 bundle in MLPPP and all T1's are up with no slips. Clock source is line for all 8 T1's and no secondary is configured. While there are no slip's, we are seeing incrementing path code violations. This typically indicates a physical layer problem, but I just want to confirm that the clock settings are not contributing to the problems.

Hall of Fame Super Gold

Re: Multiple T1s in data bundle and Clocking Domain

They may very well contribute.

First of all, verify with telco if they are supllying clock or not on these circuits. No clock supplied is common in North America.

In that case. you must provide clock at one end of the circuit.

You must have circuits 100% clean of any error for good performances.

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