E1 connection to PBX problem

Unanswered Question
Jun 16th, 2009

I am replacing an old 3600 router with a new 3800 router. the old 3600 has a E1 connection to the PBX which work fine.

The new 3800 replacement router has the same config but the layer 2 never comes up, when i do a show isdn status LAYER 2 just switches between

TEI ASSIGNED & AWAITING_ESTABLISHMENT

when i do a debug isdn q921 i get the following

Jun 16 19:45:12.031: ISDN Se1/0:15 Q921: L2_EstablishDataLink: sending SABME

*Jun 16 19:45:12.031: ISDN Se1/0:15 Q921: User TX -> SABMEp sapi=0 tei=0

*Jun 16 19:45:13.031: ISDN Se1/0:15 Q921: User TX -> SABMEp sapi=0 tei=0

*Jun 16 19:45:14.031: ISDN Se1/0:15 Q921: User TX -> SABMEp sapi=0 tei=0

Like i said the config for the E1 connection is identical on both the old and new router, I have even has the E1 card replace on the new router just in case but the problem is the same.

The funny thing is as soon as the cable is moved back to the old router it work fine.

Here is the config i am using

isdn switch-type primary-qsig

controller E1 1/0

pri-group timeslots 1-8,16

interface Serial1/0:15

no ip address

encapsulation hdlc

isdn switch-type primary-qsig

isdn overlap-receiving

isdn incoming-voice voice

isdn contiguous-bchan

no cdp enable

Serial1/0:15 unassigned YES unset up up

++++++++++

Can anyone help

I have this problem too.
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parshah Tue, 06/16/2009 - 12:19

Hi,

If you refer to the following link it explains what is happening

http://www.ciscotaccc.com/kaidara-advisor/accessdial/showcase?case=K87248376

So, in this case, I understand everything is fine when you plug the E1 in to the old routers. But when its plugged into the new one, can you confirm whether the PBX is receiving the SABMEp messages from 3800 or not?

From the debug, it looks like 3800 is sending the Layer2 msg but is not receiving any response and so layer2 stays down. CAn you find out or debug on the PBX what is happening when it receives the SABMEp msg from 3800?

Thanks,

Paolo Bevilacqua Tue, 06/16/2009 - 12:24

I think you need clock source internal and isdn network-side, not sure why it working on the old router.

freenesss Tue, 06/16/2009 - 15:46

I have tried making the changes you have suggested, but the results are the same. Layer 2 still not coming up, and the debug isdn q921 is still showing

Jun 16 23:20:54.667: ISDN Se1/0:15 Q921: L2_EstablishDataLink: sending SABME

*Jun 16 23:20:54.667: ISDN Se1/0:15 Q921: Net TX -> SABMEp sapi=0 tei=0

*Jun 16 23:20:55.667: ISDN Se1/0:15 Q921: Net TX -> SABMEp sapi=0 tei=0

*Jun 16 23:20:56.667: ISDN Se1/0:15 Q921: Net TX -> SABMEp sapi=0 tei=0

I will be getting in contact with the PBX service provider so they can check what they are seeing on the pbx side.

thanks for your suggestion and any other suggestions are welcome!

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