Port forwarding - help!

I currently use a D-Link DSL-2680 router for my broadband connection with TalkTalk. I have recently obtained a Home Signal box from Three and need to forward several ports. I have done most of these however when I try to forward port 4500 I get a duplication error. Any ideas? Is this port somehow being used for something I cannot see in my router settings? Any help appreciated as this is very frustrating!

Incidentally I have tried putting the Home Signal box in the DMZ and this didn't work.

If DMZ does not help, then port forwarding is not likely too either, as DMZ is like a port forward for every port.

It is possible that firewall settings and filters in the router may be blocking the Home Signal from working.

IPsec NAT traversal uses port 4500. I have IKE and AuthIP IPsec service disabled on my PC. Is that service running on your system, and do you need it?

More to the point, is your router using it? Wireshark can help with seeing what ports are being used.

Edited by camieabz (Sat 06-Apr-13 12:57:46)