Coming from VoIP Switch new to Freeswitch

i have Ubuntu 12.04 with static IP, installed Freeswitch with FusionPBX with easy install script from here http://wiki.fusionpbx.com/index.php?title=Easy_FusionPBX

everything is working Freeswitch , FusionPBX GUI, i have tried everything searched google , forums but didn't find any solution to this problem,

whenever i tried to register predifined Extension, for internal when trying out of the box extension 1000 from x-lite got this error

i have static IP , do i need seperate config for Static file , tried changing external ip & domain to static ip

my log

2014-03-18 20:20:56.932585 [WARNING] sofia_reg.c:1541 SIP auth challenge (REGISTER) on sofia profile 'internal' for [1000@79.143.178.100] from ip 124.155.244.195 
2014-03-18 20:20:57.392594 [WARNING] sofia_reg.c:2576 Cant register a pointer. 

please help

Thanks

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Regards,

Tushar S. Patekar