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New Member

E1 controller (Slip Errors) towards Nortal PBX

I am working on 2811 router and we have two controller cards in that, before adding the second controller card we dint have any issues on the controller card.

Setup controller 1-->>nortal PBX(1)

Controller 2 -->> nortal PBX(2)

We added 2nd controller card and we see lots of slip errors on controller 2, controller 1 is clean and we are getting clock source from the PBX. We changed the cable but still Slip errors are coming in bundles...

Basically we came to know this because our customer was not able to send the fax to that site where PBX2 is placed.

we are running IOS "flash:c2800nm-adventerprisek9-mz.123-11.T4.bin" on 2811

Is there any known bug or if someone have ever seen the above issue. Please let me know


Re: E1 controller (Slip Errors) towards Nortal PBX


is the configuration identical for both the controller cards ??

is it possible to swap the modules on different slot and check ?

Also can you connect the first pbx to the second card and second pbx to the first card and check ?

wht about the remote end configs in ur pbx side is it identical ?


New Member

Re: E1 controller (Slip Errors) towards Nortal PBX


1) Yes configuration is identical on both the controller cards.

2) Its not possible(As it is production box)

3) We already have plans to do this tonoght or tomorrow whenever we will get window, will let you know if we will find any thing.

4) Configs on both the PBX's are same apart from the version.

Just wondering if you have ever seen this kinda issue.



Re: E1 controller (Slip Errors) towards Nortal PBX

I have seen this before. And the solution varies depending on your environment.

Slips are typically a clocking issue. And while you may have "clock source line" configured on each controller, your TDM bus is likely out of sync.

Assuming the two PBXs get their clock from a PSTN carrier, all you have to do is add the "network-clock-participate" command to sync your bus with one of the PBXs. Since both of them are in sync with a carrier, you'll sync as well and the slips will abate.

If only one PBX is sync'd with a carrier, use the network-clock-participate to sync with it. And require the other PBX to receive clock from your gateway as well as configuring "clock source internal" on the controller for the non-PSTN PBX.

Finally, if neither PBX is connected to the PSTN, then require them both to take clock from you and by configuring clock source internal on both controllers.

Let me know if this helps by rating the post.

New Member

Re: E1 controller (Slip Errors) towards Nortal PBX

Hi Mike,

Thanks for the reply..

These two PBX's are not connected to PSTN at all,

Its not feasible for us to change the clock internal as there are some restrictions which customer doesnt agree to do.

Is it possible to change the clock source to internal on the faulty controller? or do we need to change both of them? As we can try for the faulty one but not the working one.

And below are the clocking commands which are in the running configs of the route.

network-clock-participate wic 1

network-clock-participate wic 2

network-clock-select 1 E1 0/1/0

network-clock-select 2 E1 0/2/0

Do reply on this one so that we can carry out this as soon as we can.

Re: E1 controller (Slip Errors) towards Nortal PBX

I can't tell from looking at your clocking statements which controller E1 0/1/0 is, the good or the faulty. I'd suspect from your symptoms that E1 0/1/0 is the good controller.

To answer your question: Yes, change the clock on your faulty controller to internal, _and_ require your customer on the faulty pbx to recieve clock from your gateway.

New Member

Re: E1 controller (Slip Errors) towards Nortal PBX

We changed the clock to internal on the faulty one. however there were just 30 slip errors instead of 200 to 250 in 15 mins time.

What is the situation here is. Both PBX's are connected to PSTN and both the PSTN are providing clock to PBX's and PBX's are providing clock to our routers. And we today we found that both the clock which PSTN are provided is not in Sync though the provider is same.

So we need to get that sync and then we will go ahead with anything, in the mean time if u have something in mind about this situation do let me know.

And the one which is clear is is E1 0/1/0,


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