I have 4 offices each with a asterisk 1.4 server. Each office has a isdn30 line and offices are connected via a 2mbit wan.
Asterisk has a sip trunk set up to link both servers via the wan using g729 codec.
We use a mix of ip phones. Phones are only connected to the local asterisk box. This system allows us to dial any phone at any office via the trunk. Works great.
My problem is:
Calls can comes in office A via isdn30 and then get transfered via the sip trunk to a member of staff at office B. If then office B transfers it back to a member of staff at office A we have the call going twice over the wan.
Is there any way to improve on this and have the call only going once over the wan via some clever extension etc . We do find we can get reduced quality due to this.