A few days ago I had a problem with a couple of extensions. I have about 12
Aastra 6731i phones, 6 are at our main office and 6 more on remote branches. We use VPN to communicate to our branches so there’s no NAT
involved any where.
The problem I had was that I couldn’t call from two extensions located at two branch offices. But I could call to them just fine. On any call placed from those phones I got the following error:
SIP/2.0 401 Unauthorized
This is the console output of a call placed from one of those phones: