IPv6 and why email did not work any more

Christian Stredicke
CEO of Vodia Networks

So everything that we buy these days should be ready for IPv6. snom ONE supported even in the old pbxnsip times already IPv6. Nothing new here.

While we are all waiting for the happy day when our service providers finally give out publically routable prefixes so that all out phones in the LAN don’t need NAT any more, we need to deal with some more down-to-earth problems. One of the problems is that DNS uses records for IPv4 and some others for IPv6 (A and AAAA).

While practically all services in the net offer IPv4 DNS addresses, there are more and more providers that also add AAAA records. The problem is that a DNS server operates independently from the underlying internet version. In other words, you get AAAA records even when the DNS server is running on IPv4. The practical problem is that a client is running in the LAN without any IPv6 connectivity to the outside world also gets those AAAA records. When it then tries to connect to the service, it eventually times.

That is exactly what happened with Gmail. Google added IPv6 records for the Gmail service some time ago, and suddenly the snom ONE email client did not work anymore if your PBX did not have IPv6 connectivity.
The way we fixed the problem is that the PBX now looks at the IPv4 records first. I did not use the world “solve the problem”, because this is not a proper solution. The day that IPv4 will become unavailable to the PBX, this fix will not work anymore.

But I guess we will have a few more years to properly solve that problem. For now we can live with the workaround, and hopefully the snom ONE users will not notice anything.