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Clocking with multiple types of external connections?

Clocking with multiple connections.

I need some help on figuring out how I should setup clocking in the below scenario. In back of this router is UCM Business Edition.

Customer has 2851 with four vwic-mft-t1's (only three in use) and one NM-1CE1T1-PRI

0/0/0 - will have a PRI

0/0/1 - Crossover connection to NM-1CE1T1-PRI (use to get modem calls in from PRI over to NM-1CE1T1-PRI and onto onboard PVDM2-12DM modem module).

0/1/0 - T1 to Frame-relay carrier

1/0 (NM-1CE1T1-PRI) connects to 0/0/1 and sends modem calls to PVDM2-12DM

In a scenario like this where you have external connections to different services (PRI and Frame-relay) then you have another back to back configuration (modem work around) what is the optimum clocking setup?

Thanks in advance


Re: Clocking with multiple types of external connections?


The clocking of E1/T1 controllers can be set up individually. If you have connection from external providers the best way to set the clocking to recover it from the line (provider).

So for

0/0/0 clock source line

0/0/1 clock source line

0/1/0 clock source line

Oen question:

If the 0/0/1 connected directly to 1/0 where is the PRI connected to receive the calls?

Hope it helps, rate if does



Re: Clocking with multiple types of external connections?

Hooking ports back to back on the same router is not the best idea but PRI and modems are not my best topic.

As you have found out doing this causes all kinds of issues with the clocking. Not sure you can 100% fix it but at least the ISR line of routers give you a chance.

You need to sync the router chassis to the best clock you have.

There are 2 commands that do this.



First take any line that is not related to this issue and set them to NO network-clock-participate and set the clocks to LINE.

Now take the line that has the best clock and set it using the clock select. This will make your router internal clock sync to that line.

You now take all the other boards and set them using the network clock participate to use that clock. Normally you then take all the lines that have issues and set their clock to internal which if all works well syncs it to the selected line.

In your case because the data is passing in and out of the router multiple times you may have to set the last board to not participate with the router internal clock and get its clocking from the line which of course is just the internal clock. I would first attempt to sync everything to the real PRI and see if it works.