So I have a PBX Server set up and need to forward ports 10000-20000 however when I access my router settings it doesnt let me forward such a large range of ports it limits it to around 10000-10135. Any help on how I could open such a large range would be appreciated.

The [NAT] > [Open Ports] section allows forwarding a range of ports and should allow you to open ports 10000 to 20000 to that device.

The [NAT] > [Port Redirection] entries do also allow for setting a range but this has a different function in that it maps a single port to a different LAN IP. i.e. opening 10000 to 10135 will open port 10000 to 192.168.1.10 and port 10050 to 192.168.1.60.

Thank you for your help. Managed to get the ports open and now my voip system seems to be working.