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Clocking Query for E1 Controller

Hi guys,

Only new to the world of clocking so be gentle :-)

I have inherited 4 x 3745 voice routers and am trying to understand why the network clocking is configured the way it is.

On one of the routers there is:

network-clock-participate slot 2

network-clock-select 1 E1 2/1 (this is to the PSTN)

network-clock-select 2 E1 2/0 (this is to our internal PABX)

This makes sense to me that we are taking the clocking from the external service provider.

The other 3 x 3745 routers also contain multiple E1 connections to the external PSTN and internal PABX but are configured to use the backplane for clocking.

i.e. no network-clock-participate for all slots.

From what i have read you are better off using the PSTN connection for clocking rather than the backplane.

There are no slip second errors at all and everything is working fine but I am wondering should i be changing the other three routers clocking sources as a best practice type exercise.

I also have to add a new E1 connection to an internal PABX on one of the routers using the backplane for clocking (with a connection to the PSTN) and am wondering if i leave it as is and use the no network-clock-participate slot for the new card.




Re: Clocking Query for E1 Controller


A couple quick questions -

Are all of the external PSTN connections going to the same carrier?

If so are they going to the same CO switch (to your knowledge?

I don't really understand why they would have you PABX as the second clock source - normally you would use a second line to the carrier and the PABX should be clocking from the router via a participate command

Does the PABX have another E1 directly to the carrier?


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