Router 2821 with VIC2-2BRI-NT/TE and 12(4)9T1 have some problem

Unanswered Question
Mar 8th, 2007

Hi friend,

I have the router specified in the title with that IOS version and that VIC. The problem is that the voice port are unable to work as Network for a PBX. Before this type of router the architecture was builded with a Cisco3640 and a VIC-2BRI-ST/TE and all work good. What can be the problem?

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Overall Rating: 4 (1 ratings)
Paolo Bevilacqua Thu, 03/08/2007 - 10:14

Ah forgot to mention, the VIC-2BRI-ST/TE does not support network side, so I'm not sure how this was working previously.

matteo.margheritini Fri, 03/09/2007 - 09:03

Hi friend, with a q921 debug i can only see RX, it seems that my router don't send TX. If i activate a q931 debug i can't see nothing. A call from a phone on the pabx not result on the router. what are the differences between the two VIC?

thx for all

Paolo Bevilacqua Fri, 03/09/2007 - 09:10

Very strange that the router does not do TX, to see whta is going on, you can post the trace here, together with configuration, show controller, show isdn status.

The main difference is that the older card does NOT support network side, the newer does.

For this you need an ISDN BRI crossed cable (NOT an ethernet crossed cable).

andrey.smirnov Mon, 03/12/2007 - 01:05

I experienced the same problem a couple of weeks ago with exactly the same configuration of hw/sw. It's just a bug in IOS 12.4(9)T1. I'm not sure that the bug was fixed in 12.4(9)T2 but the latest IOS 12.4(11)T1 has no such problem.

Best Regards,


matteo.margheritini Mon, 03/12/2007 - 08:39

thanks a lot, i will give to you an answer as soon as possible because i must fix this problem. If I don't solve the problem, i will post all the things that Mr.Bevilacqua said.

Paolo Bevilacqua Mon, 03/12/2007 - 09:22

Matteo, often IOS have bugs, and upgrading to latest 12.4(9)T or 11T or even 11XJ is a good idea.

However, I do not understand how you were able to work in network side with the VIC-2BRI that does not support that, and you have not said which kind of cable are you using, so it is quite possible that you have physical problem instead.

matteo.margheritini Mon, 03/12/2007 - 10:03

Yes, in the old router I have two TE Basic Rate Interface in a NM-2V, and in the configuration of the interface Bri there are this two command

isdn protocol-emulate network

isdn layer1-emulate network

they let me think that they work as network side with the PBX!! The Cable is a straight-through cable and pins are: 4 Blu 5 W-B 3 Orange 6 W-O.

Paolo Bevilacqua Mon, 03/12/2007 - 13:39


first of all if the card you had previously was really VIC-2BRI-S/T-TE, that do not supports network side, no matter the commands in configuration. But if it was a VIC-2BRI-NT/TE, yes that supports network side. See:

Second, you really need a crossed cable to connect to a PBX. Please see:

Also check with the PBX manual what is the pinout.

Finally, if you take the trace with debug isdn q921, show diag, show run and show isdn status, we can tell what is going on.


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