im having my FS box behind NAT, the network topology is something like: IP PHONE A(Public IP)<------->NAT<------>FS(Private IP, with a public IP)<------->IP PHONE B(Private IP) i was trying to have IP PHONE B able to make call to IP PHONE A and have two-way talk. with the default FS configuration when IP PHONE B calls IP PHONE A, there's only one-way talk, A can hear B but B cannot hear A. then i decided to use stun by modifying: vars.xml <X-PRE-PROCESS cmd="set" data="external_rtp_ip=stun:stun.freeswitch.org"/> // this is the default config <X-PRE-PROCESS cmd="set" data="external_sip_ip=stun:stun.freeswitch.org"/> // this is the default config internal.xml <param name="ext-rtp-ip" value="stun:stun.freeswtich.org"/> <param name="ext-sip-ip" value="stun:stun.freeswtich.org"/> external.xml <param name="ext-rtp-ip" value="stun:stun.freeswtich.org"/> <param name="ext-sip-ip" value="stun:stun.freeswtich.org"/> but while restarting FS, there's error reporting: 2013-08-08 10:33:58.933096 [ERR] sofia_glue.c:1043 STUN Failed! stun.freeswitch.org:3478 [Bind Error!] 2013-08-08 10:33:58.933096 [ERR] sofia.c:4074 Failed to get external ip. 2013-08-08 10:33:58.934072 [NOTICE] sofia.c:4754 Started Profile external [sofia_reg_external] ... 2013-08-08 10:34:00.859927 [ERR] sofia_glue.c:1043 STUN Failed! stun.freeswitch.org:3478 [Bind Error!] 2013-08-08 10:34:00.859927 [ERR] sofia.c:4074 Failed to get external ip. 2013-08-08 10:34:00.860904 [NOTICE] sofia.c:4754 Started Profile internal [sofia_reg_internal] so am i still missing some configuration or anything else was wrong?