Wi-Fi calling is pretty much an IPsec VPN from the cellular device to the carrier.
While I don't have a list of IPs some quick googling did find some form post with domain names and IPs block for some carriers. The main thing is making sure IPsec is not blocked or is otherwise not interfered with or broken. Of course this is mainly going to be UDP Port 500 and 4500. Apparently also port TCP 143 (IMAP) may also be used for some for some reason for some carriers, Not 100% clear on that one. Brandon Jackson bjack...@napshome.net On Fri, Aug 2, 2024, 11:48 <chuckchu...@gmail.com> wrote: > Hey all, > > > > Question if anyone knows about cell phone wi-fi calling in > US. Googling isn’t finding what I’m looking for. We have a corporate site > in US where users have BYOD capability, and use their phones with wi-fi > calling enabled. Site uses a single NAT address (IPv4) for BYOD access. > Recently the site reported wi-fi calling had stopped working for all user > phones, Apple and Android, all about the same time. The guest network did > have some bandwidth limitation applied and they had overuse. That was > since resolved, we upped the bandwidth. But the phones all still avoided > wi-fi calling. It’s a manufacturing site with known cell signal issues, so > most users had no signal via carrier. I did not get a packet capture yet > to see what could be going on, we’re 99% sure we’re not blocking traffic. > I’m wondering if the phones have an algorithm to test wi-fi signal, and > perhaps the carriers will blacklist public IPs with known wi-fi calling > issues to avoid cases where an emergency call can’t be made because of > intermittent bad performance? It seems odd that even when no bandwidth > issues exist, it’s not attempted. > > > > Thoughts? > > > > Thanks, > > > > Chuck Church >
