In our university environment, wifi calling works just fine over NAT and we have not made any inbound port exceptions in the firewall for it. The critical piece for (non-enterprise) VoIP traffic is that your firewall must not try to function as a SIP ALG, but I'm not sure that's directly relevant to wifi calling for the major carriers.

Jason Alderfer
Director of Technology SystemsEastern Mennonite University

On Fri, Jul 17, 2020 at 12:40 PM Lyden, John C <lyden@rowan.edu> wrote:

Hey gang.

We’re setting up a unified wireless network for the students here, and to get around the issues with Nintendo and NAT we devoted a large chunk of public IP space to them.

We’re aware that this is causing issues with wifi calling on Verizon, TMo etc because it appears they initiate the SIP session inbound.

Does anybody have a handy list of IP blocks and ports? T-Mobile had a decent page but other providers just said “open up 4500 and 500” and our ISO guys don’t like that.

Thanks if someone can help.

John C. Lyden

Manager of Network Infrastructure, Infrastructure Services

Division of Information Resources & Technology, Rowan University