E1 errors

Unanswered Question
Apr 8th, 2009


I have these problems on E1 link with my PSTN provider:

1) sometimes, when I make an outside call, I hear that the other side answers but the call drops immediately

2) sometimes when I make an outside call, I receive the busy signal. I notice that we are never used all the channels of E1 link.

These are our architecture:

- Cisco Call Manager v.4.1 sr.7

- Voice gateway Cisco 2851 IOS spservicesk9-mz.124-8

- E1 connection with PSTN provider via MGCP and VWIC-2MFT-E1 module

as attachments, there are today reports from "show controllers e1" and RTMT.

In these outputs I notice some errors.

Is it possible that the problems that I've listed are connected with these errors?

thanks in advance


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cisirunite Wed, 04/08/2009 - 01:43


these are the lines:

network-clock-participate wic 0

network-clock-participate wic 1

network-clock-participate wic 2

network-clock-participate wic 3

network-clock-participate aim 0

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

network-clock-select 2 E1 0/1/0

network-clock-select 3 E1 0/1/1

network-clock-select 4 E1 0/3/0

network-clock-select 5 E1 0/3/1

The interested E1 interface is 0/0/0.

cisirunite Wed, 04/08/2009 - 01:54

do you know if i could execute other commands to show these problems to the provider?

Paolo Bevilacqua Wed, 04/08/2009 - 02:01

No, just show the errors in "show controllers".

Likely the will still say that everything is fine, so you have to insist, ask for a 24 bert test, etc.

cisirunite Mon, 04/27/2009 - 04:37


in relation to the problem that I've explained in the first post, my provider tells me to configure my router to ask for an outbound channel to the PSTN instead of choosing it by myself.

Do you know if it is possible? What is the command?



Paolo Bevilacqua Mon, 04/27/2009 - 04:40

Please submit output of "debug isdn q931" with 'term mon" to prove thta router is using exclusive b-channel selection.

cisirunite Mon, 04/27/2009 - 05:10

This are the results:

71783: Apr 27 15:11:45.499: ISDN Se0/0/0:15 Q931: RX <- CALL_PROC pd = 8 callref = 0x83E4

Channel ID i = 0xA9839C

Exclusive, Channel 28

Progress Ind i = 0x8288 - In-band info or appropriate now available

There are other output like this.

Do I have to configure the command "isdn-negotiate bchan"?



Paolo Bevilacqua Mon, 04/27/2009 - 06:56

It depends, if you're using MGCP, the isdn commands under interface have no effect.

However from the trace you sent, nothing shows that calls are failing due to exclusive selection being used.


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