FAX Server (BRI) not working after H.323 GW upgrade 2651->2811

Unanswered Question
Oct 27th, 2009
User Badges:

Hi Everyone,

I just finished a Call Manager upgrade for customer from 4.1.3 to 7.1.2. As a part of the upgrade, we also upgraded their H.323 Gateway from 2651XM running 12.3 to a 2811 running 12.4.25b.

After the gateway upgrade faxing stopped working. They are using a Brooktrout fax server that runs on a Windows 2000 server with a 2x BRI card in it. Here is how it connects into PSTN:

FAX Server-BRI --> VIC2-2BRI (2811) --> NM-HDV2-2T1/E1 (2811) --> PSTN

At the moment faxes do occasionally go out (about 50% of the time), but nothing comes it. Calls do go in and out of the gateway (G.711u-law) and the fax starts training up, but after 3x tries it gives up logging a communications error: “DCS sent 3 times without response”. Fax server vendor suggested that it could be either clocking/slips related or due to compression (anything less than g.711) when sending faxes in and out.

The config has not changed from the 2651 to the 2811 apart from the E1 clocking. They did not have any clocking configured and had some E1 slips. After the upgrade I noticed the slips on both E1 controllers so I configured the clocking:

network-clock-participate slot 1

network-clock-select 1 E1 1/0

I have also tried the following commands individually without any success:


dial-peer voice 100, 101, 200, 201, 301 pots

fax rate voice


dial-peer voice 100, 101, 200, 201, 301 pots

fax rate disable


dial-peer voice 100, 101, 200, 201, 301 pots

fax rate system


voice service voip

fax protocol none

modem passthrough nse codec g711ulaw

The problem still remains: Fax server does connect, but does not train-up to the other end failing with the communication error.

I have attached the gateway config. I appreciate any suggestions.

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
art.tumanik Wed, 10/28/2009 - 00:28
User Badges:

I found a solution to the problem.

I had to add compand-type a-law under each BRI voice port. That fixed all faxing issues.


This Discussion