We're seeing this same exact issue with a number of our phones (specifically CounterPath Bria for iOS and others). Calls placed disconnect after ~1:48 on some NATs, (specifically our wireless data carrier, AT&T 3G). http://lists.freeswitch.org/pipermail/freeswitch-users/2012-March/081317.htm... In freeswitch, the CLI shows: 2012-08-27 00:41:59.471201 [DEBUG] switch_core_session.c:1429 Session 174 (sofia/internal/2000@mydomain.com) Locked, Waiting on external entities 2012-08-27 00:41:59.471201 [NOTICE] switch_core_session.c:1447 Session 174 (sofia/internal/2000@mydomain.com) Ended 2012-08-27 00:41:59.471201 [NOTICE] switch_core_session.c:1449 Close Channel sofia/internal/2000@mydomain.com [CS_DESTROY] 2012-08-27 00:41:59.471201 [DEBUG] switch_core_state_machine.c:514 (sofia/internal/2000@mydomain.com) Callstate Change HANGUP -> DOWN 2012-08-27 00:41:59.471201 [DEBUG] switch_core_state_machine.c:517 (sofia/internal/2000@mydomain.com) Running State Change CS_DESTROY 2012-08-27 00:41:59.471201 [DEBUG] switch_core_state_machine.c:527 (sofia/internal/2000@mydomain.com) State DESTROY 2012-08-27 00:41:59.471201 [DEBUG] mod_sofia.c:374 sofia/internal/2000@mydomain.com SOFIA DESTROY 2012-08-27 00:41:59.471201 [DEBUG] switch_core_state_machine.c:86 sofia/internal/2000@mydomain.com Standard DESTROY 2012-08-27 00:41:59.471201 [DEBUG] switch_core_state_machine.c:527 (sofia/internal/2000@mydomain.com) State DESTROY going to sleep We fixed this by shutting of the "Passive Session Timer" in the "SIP Miscellaneous." However, I'm curious to know if anyone can explain why this happens on some NATs and not others? Is there s problem with disabling the "Passive Session Timer" on our clients? -Rob