I have a GXP-4018 with 8 pstn lines and I used the guide here to set it up: http://www.freepbx.org/forum/freepbx/tips-and-tricks/how-to-grandstream-gxw-4104-setup
I tried posting my question under that guide but received no response, so trying again here.
When I set up my outbound rules on free pbx, I tell free pbx the order in which i would like the pstn lines to be used in. I would like to choose which of the PSTN lines will be used when making outbound calls. But it seems like the GPX-4108 always uses first channel 8, then channel 7 if channel 8 is busy, then 6 is 7 is busy, etc…
There must be something wrong in the config of the GXP-4108 since Free pbx does route other outbound routes correctly (i have some other voip trunks for long distance).
Any help would be appreciated.
Have not tested it but pretty sure I found the setting that fixes this and though I would post in caase anybody else has the same problem. This link was very helpful:
In it you can find this area which describes the settings needed.
Port Scheduling Schema (VOIP->PSTN)
1. Round-Robin and/or Flexible:
You have two choices here:
Choice #1: If you want each phone line to have its own trunk, you can set-up four different trunks in FreePBX, and then set-up each outbound route to specify which lines get which outgoing calls in which order. Set Round Robin as follows:
Round-Robin and/or Flexible: rr:1;rr:2;rr:3;rr:4;
Choice #2: If you want all phone lines to come in and go out on a single trunk. This means that your PBX will have one trunk, and the GXW-4104 will decide which line to send calls out. Generally, the GXW-4104 will send out all calls in accordance with your round-robin settings (see below), by using the highest numbered line in the round robin first. Set the Round Robin as follows:
Round-Robin and/or Flexible: rr:1-4;
2. Prefix to Specify Port: 99