[Serusers] record_route() & record_route_preset() di

Hello, I have a question regarding record_route() & record_route_preset() functions. I faced up a problem with some SIP clients with inbound calls where I believe that it's related with these functions. 1/ When I use the "record_route()" function in a single server SER setup I have the following "Record-Route:" header in INVITE mesg from SER to called SIP UA: Record-Route: <sip:1.2.3.4;ftag=AAA-19972;lr=on> ... 2/ When I use the "record_route_preset()" function in a double server SER setup (2 SER servers behind a Cisco CSM Load balancer), example : record_route_preset("5.6.7.8"); I have the following "Record-Route:" header in INVITE mesg (SER -> called SIP UA): Record-Route: <sip:1234567890@5.6.7.8;ftag=XPH-5307;lr=on> ... In first case the SIP UA accepts the inbound call and everything is Ok. In second case the same SIP UA doesn't replied with '100 Trying' mesg back to SER. In the second case, SER also adds the called number "1234567890" in the Record-Route header. Why there is this difference and if that can cause problems (incompatibility) to some SIP clients ? thanks for any hint, Kostas