We have a Vigor2830 which we are using for VoIP/SIP traffic. One of the ports needed is 5090 TCP/UDP. We've opened this port from NAT > Open Ports in the menu but when we check this port from an online port checker, it is showing as TCP closed and UDP open.

Other ports which are open on the router are:

5000 TCP
5001 TCP
5060 TCP/UDP
5061 TCP
9000-9500 UDP
389 TCP/UDP

Has anyone else experienced this issue and if so are there any solutions?

Thanks in advance.