Is there any phone device configured to already use 5060?

I am pretty sure that the Draytek would not block 5060 or any PORT.

Nope, definitely nothing else using 5060.

I am having the same/similar issue. YOU cant do a Telnet to the port since 5060 is UDP not TCP. But i did try nmap and the port is definatly open, but no phones from the outside of the WAN can register to the internal IPPBX.

As this router is a V model, it has built in VOIP and so by default the router is programmed to flow all VOIP traffic to the actual router itself.

Trying to bypass this feature to forward the port to a different server will result in the issue you are experiencing as whilst VOIP is enabled on the router, the router will not forward the traffic to another destination.

You must first disable VoIP on the router and this should cure the issue!

Hope that help!

The Vigor2820Vsn has a port mirror facility that would could use to see if the traffic is being forwarded to the pbx.

It's set via telnet. Te command is

>port sniff ?

Set the txtx port to be the port that connects to you phone system and then connect a PC to another port P4 for example and set p4 as the mirror port. Then run wireshark on that PC. Note, the mirror port is cut off from the network.