- An external SIP user A makes a call to an internal user B (SIP, ISDN or analog).
 - B makes an additional call to an external user D.
 - If both external users A and D can be reached via the same SIP line, the LANCOM VoIP router delegates the administration of the call forwarding to the upstream provider.
 
Note: Requires that the VoIP PBX fully supports Transfers in SIP (re-invites).