Hi,

while testing IPv6 with customers, we fell over quite a few cases, where customers aren't reachable on inbound calls most of the time. And digging into this, we found the home router firewall as the cause for those problems.

Normally, you would think, all the NAT problems cease when switching to IPv6. But actually, right now I don't know how to fix that problem.

In IPv4 NAT scenarios, we would flag the customer during the registration, and Kamailio would send NAT pings (those 4 bytes of UDP junk) every few seconds to keep the firewall in the NAT router open. And that worked pretty great.

Now we have IPv6. We don't have NAT. But we still have a home router in front of SIP devices, with a firewall. And this firewall will allow outbound traffic. But after a few seconds it won't allow incoming connections anymore. And the routers I have seen so far don't have a configurable firewall where you could allow inbound traffic from our server.

Unfortunately, only our load balancer is IPv6, our registrar is still IPv4 only. And the loadbalancer doesn't know anything about registrations and which customer needs an IPv6 keepalive.

Does anyone have a hint, how to keep the IPv6 registrations alive? Thanks in advance.

Best Regards,

Sebastian