/GXW 4104 / GXW 4108 – Choosing Outbound Ports

GXW 4104 / GXW 4108 – Choosing Outbound Ports

Hi All

We are currently installing a Trixbox based VoIP system for a client in the UK. For those of you who don’t know – The system is a software solution that runs on PC hardware.

In order to connect the VoIP system to the POTS (Plain old telephone system) we are using a Grandstream GXW 4108 Gateways. These little devices allow us to simply plug in the PSTN telephone lines (up to 8 on this particular device) and have them connect to the VoIP system over the IP network.

Grandstream GXW 410x

The problem we were having was directly calls to specific telephone lines on the GXW 4108. Our client runs several businesses and when they make a call they want to ensure that the correct telephone number shows up for the caller id, plus the billing needs to be assigned to the correct business.

Here is our setup :

Line 1 – 01234 123456 (this is the line for business 1)

Line 2 – 01234 123457 (this is the line for business 2)

Getting the VoIP system to direct the call to the GXW4108 and then use the correct line was giving us some difficulty. The documentation didn’t help and Google wasn’t much better. However ¬†we did eventually figure out how to set things up:


Under the Channel config page, almost at the end there is a field:

2. Prefix to specify port (this has the number 99 as a default number)

So to dial any specific line – you prefix the number with 99x (where x is the port number you wish to use)

As an example, if you want to dial 123456 using line 2 you would dial : 992 123456, for line 3 you would dial 993 123456

By using dial rules on the Trixbox trunk we are able to automatically add the correct prefix (so the caller does not have to remember to do this).

Anyway hope that helps someone else with the same issue.

Let me know if you need any example configs or help with your setup.