Question : Fax and Cisco VGC248

We have installed a Cisco VOIP system to replace out old PBX. Overall we are very happy, but we have a nagging problem.

We interfaced our old analog phones. modem lines, and faxes to the new system using VGC248 gateways. About 99% of the time faxing works perfectly. However, there is a small number of faxing destinations that cause problems. Whenever we fax to these 5 or 6 locations, the fax fails. The machines do connect, but the transmission fails. I have trying playing with the line levels to no avail. The problem is reproducible when we fax from other fax machines in our system. However, when we fax from a fax machine connected to a dedicated CentraNet line, the fax works perfectly.

I imagine, there is a setting that needs tweaked, but neither our consultants or I can find it. Any ideas?

Answer : Fax and Cisco VGC248

Jim,

The answer is yes you have to set up the configs to allow for faxing, here is a link to a previous post of mine in regards to same problem:

http://www.experts-exchange.com/Networking/VoIP_Voice_over_IP/Q_21188399.html

The problem is that if you are using any other codec than G.711 for faxing the inband signaling of the fax tones become distorted.

Can you post your router configs?