Can't pick-up inbound calls

Unanswered Question
Sep 18th, 2008

Hi I'm setting up a new voice gateway in UK. We have 3 BRI from BT. The problem is that I cannot pickup the inbound calls. Placing outbound calls isn't an issue.

We have 10 DID / DDI from BT.

The gateway is configured as a H.323 gw back to our CCM 4.2(3)

I can se the calls comming in when debuging isdn q931.

I've done this set-up in other European coutries before without any issues.

Is the BT ISDN BRI diffent from other operators?

Can some one se something faulty in the configuration?

Whats the next step to troubleshout?

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
wboonshen Thu, 09/18/2008 - 19:03

What do you mean that you can't pick up inbound calls? Does the phone rings when a call is made? Anyway the things that you can check is the Inbound calls calling search space on your gateway configuration in your callmanager. Make sure it's set to a CSS that's allowed to reach the phones.

cg100668 Fri, 09/19/2008 - 01:35

Hi,for BRI calls, BT normally sends 5 last digits, however BT can also modify the settings to send only 4 digits. If your extension number is 3 digits, then you have to created translation rules in the H323 gateway or you can set CCM to receive 5 digits and create the translation pattern in CUCM.

Hope this will help you.


lennarth_seland... Fri, 09/19/2008 - 03:20

BT sends 6 digits. Looks like BT is doing something weird. I see the call comming in twich on the phone at the same time. That is also seen in the the ISDN q931 debug. It somes in on two BRIs. If I shutdown all BRI except one. It works fine. I rings and I can pick-up the call.

Any idea what's going on?

cg100668 Fri, 09/19/2008 - 03:32

It looks like you have only 1 physical BRA line with 2 channels. You have most probably connected the 2 RJ-45 ports from the NT box to 2 BRA ports on the router. That is why you are seing 2 calls coming in when you run ISDN q931 debug. Just connect one cable from NT1 box to the BRA port. If you are expecting another BRA line, please look for another physical line.


craig.corbett Tue, 09/23/2008 - 07:20

I had a similar issue, turned out to be a BT-ism.

I had to remove isdn static-tei 0 from each BRI interface. Something to do with how they configure multiple BRI. I had this issue when I tried to use BRI trunk, then had the config with static-tei then figured out had to remove it.

Specifically I have my BRI interfaces configured like:

interface BRI0/1/1

no ip address

isdn switch-type basic-net3

isdn tei-negotiation first-call

isdn point-to-point-setup

isdn incoming-voice voice

isdn calling-number .


craig.corbett Mon, 09/21/2009 - 02:23

Rod, take a look at this post:

Posted by: ian.perry - Network Consultant, Comstor - Mar 25, 2009, 9:10am PST

If you have DDI numbering on an ISDN2, especially BT, you need a static TEI value of 0 (point-to-point)

If you have single number or MSN numbering, leave your TEI assignment as dynamic (point-to-multipoint).

Hope this helps,



This Discussion