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I am having trouble with port forwarding on my Netgear Nighthawk X8 (R8500) wireless router. It is currently running the latest firmware version (1.0.2.94). I have a Cisco 7960 IP telephone running SIP firmware that I am trying to use with a VoIP provider. I can send calls with no problem, but I cannot receive incoming calls. I used a softphone to narrow the issue and have found that it has something to do with my setup so it lead me to port forwarding. I created a port forwarding rule for port 5060 which is the correct port for the service I am trying to use. My ISP doesn't block this port. I also assigned the phone a static IP address before I created the port forwarding rule. The rule is using UDP and not TCP since VoIP uses UDP. I am still not able to receive calls, and I checked to see if this port is open by using multiple port checking websites. They all indicated the port is closed. I already tried rebooted the router. I am not sure what else I can do.
I performed a test using my computer with a softphone to see if the port forwarding was working at all and it did in fact work. So at this point, it looks like it is the IP telephone that is the problem. According to the configuration, it is listening on port 5060, but for some reason it is not passing the port test. At least I know at this point that the port forwarding rules in general are working.
Yes, the SIP service I use only uses port 5060 and the telephone is configured to use 5060. I did try the suggestions you mentioned before regarding toggling the SIP ALG and trying the TCP/UDP setting. It didn't make a difference. Regardless of how I set it up, I still cannot receive incoming calls but ultimately the websites that check the ports keep telling me that the port is closed.
I forgot to ask the other key question. Does your R8500 have a public IP address on its Internet port? A lot of ISPs are switching to private addresses using CGNAT (Carrier Grade NAT). If this is the case for you, then port forwarding won't work. You would need to lease a public IP from your ISP.
I believe that it is a public IP address. I read that my ISP is not employing the use of CGNAT. I found a webpage that has a test to see if you are likely behind a CGNAT address and the test showed that I am not.
I performed a test using my computer with a softphone to see if the port forwarding was working at all and it did in fact work. So at this point, it looks like it is the IP telephone that is the problem. According to the configuration, it is listening on port 5060, but for some reason it is not passing the port test. At least I know at this point that the port forwarding rules in general are working.
