SNOM m9 VoIP phone just works using IPv6 with a FireBrick FB2500 VoIP call server.
I was expecting to have to tweak something or diagnose something one way or another, but no - we plugged it in - set the identity (server, username, password), and it works - incoming and outgoing calls - using IPv6.
We'll do a few more tests, but so far I have to say well done to SNOM!
The FireBrick handled the call and bridged the media between IPv6 and IPv4 with no problems.
We just need a simple cheap desk phone that does IPv6 now, please, snom...