This configuration has been submitted by a Gradwell user, and is not supported by Gradwell technical support at this time.
trixbox CE will work fine behind NAT, but it will need the correct ports forwarded from the router and usually needs an addition into the conf file of sip_nat.conf.
Be sure the LAN/private address is statically assigned to the trixbox server and it is not assigned dynamically via DHCP. UDP Port 4569 is used for IAX communications. UDP Port 5060 is for SIP communication. This is only used for setting up calls, taking down calls and so on.
UDP Port 5060-5082 range is also for SIP communications. Some phones (i.e. Grandstream GXP-2000) don't use the same SIP port for each subsequent line (line 1 registers with 5060, line 2 5062, line 3 5064 and line 4 5066).TCP Port 5060 is for SIP but thought to be rarely used. UDP Port 10000 - 20000 is for RTP - the media stream, known as the voice/video channel.
The sip_nat.conf file should look like:
externip = 126.96.36.199 (enter your permanent WAN/Public Internet address here. Or you if you have one, you can use a DynamicDNS domain name. However, it is easier to get a static IP address and avoid using DynamicDNS altogether.)
If you are using a dynamic DNS domain name, you should rather use:
externhost = home.mydomain.com
externrefresh = 5 (lookup hostname every 5 minutes to refresh IP address)
localnet = internal.network.address/255.255.255.0 (replace internal.network.address with your base network address e.g. 192.168.2.0 and not the IP of the Trixbox)
Once the changes have been made, click the Update bar and reboot your machine.