I have a Cisco 2811 (CME) and it is registering with an external SIP provider (ITSP) for external calls.
I am also trying to setup SIP extensions to run over a VPN to a remote site. The 2811 ISR is doing the SIP trunk termination, CME SIP registrations and the IPSec VPN Tunnel.
What is happening, unless I add the command below, the SIP phones cannot register
voice service voip
bind all source-interface fa0/0.1 (which is the internal VLAN)
However, when I add this command the SIP trunk to the ITSP drops and doesn't work.
Does anyone know how to fix this?