Hi, i have recently purchased a 2960 router to use in a dual wan setup. I have 2 phone lines coming into my house from the same ISP (Plusnet) and they both have a static IP addresses. Previously i had an Asus RT-AC87U and never had this problem until i switched over to the vigor.

I have ubiquiti wireless APs throughout my house and so this issue shouldn't be related to signal strength. I have a pretty stock configuration, with just a couple of port redirections and lan DNS profiles. To be honest, this router is well above my technical ability, but i chose it as it has the dual wan functionality i needed.

The reason for wifi-calling is that where i live the phone signal is really poor (Three/o2) and so I rely heavily on this. When i make or receive a call it will initially connect and then about a second later it will fail. If i try repeatedly 3 or 4 times it will eventually hold and then i can talk indefinitely. interestingly it doesn't fail on every call, making this even more frustrating, but certainly most of my calls will fail.

It's as though in that initial handshake, something fails (ports?) and the call drops. Apple gives a list of all the ports their services use and according to this wifi-calling uses UDP 500 and 4500. I don't know how to open these ports on all devices, but only as a redirection to a device with a static ip address.

Any ideas/help will be greatly appreciated! Can anybody else with this router makes/receives calls successfully. I have emailed technical support and they don't believe those ports need to be opened.

Many thanks!

Whilst I can't say why your calls are failing, I can say with reasonable confidence that you do not need to open any ports on your router.

https://support.apple.com/en-us/HT202944 suggests that 500/udp and 4500/udp are used as part of IkeV2 exchange for Wi-Fi calling. That should work outbound through NAT. There is no way to open a port for 'All devices behind NAT', as the router would not now which internal device to forward a received packet on that external port to.

Thinking about it, those ports are also used as part of VPN negotiations. You could check that on your router all VPN functionality is disabled (so that it does not conflict with the iPhone traffic).

thank you for responding, i've been pulling my hair out for weeks!

well, you might be on to something here! I did have VPN enabled (not that i've ever used it) and so turned that off and it seems to be working! I'll keep monitoring it this week, but i've just tried it 30 times and it didn't drop once.

well, back to the drawing board, as just had 2 "call failed".