I've set up a client with the new 2850n, along with an iMac and 2* Yealink T22P IP phones.
The phones register fine to voip.co.uk for a few hours then start to show "register fail". Internet access is still OK on the Mac. Restarting the phones doesn't fix the problem but rebooting the router does - for a few hours at least.
Phones and router are running latest firmware (3.6.1).
So far I have tried disabling the firewall and opening TCP port 5060 and UDP ports 10000 - 20000. None of this helps.
This evening I have moved one phone to SIP port 6060 to see if that helps. I've also turned off UDP keep alive (SIP re-registrations are set to ~90 seconds) to see if this helps.
I think it's a bug in the 2850 but wanted to see if anyone has had success with this - I note on the forum the 2850 isn't the first Vigor router to cause difficulties.