I have the following weird issue. A Cisco router is connected to a VPN 3000 concentrator and on the remote LAN we have some phones. The issue is that the 'old' phones (7912, 7940) work fine. The new phone's (7911 7941) do not work. They do appear in the callmanager as registered, when you click on the IP of the phone you see that all seems OK except it has no DN. The DN field is empty.
When this phone is connected directly on the LAN it works fine.