Hi,
Thank you for the reply!
I tried advertising udp port like this listen=udp:192.168.1.x:5060 advertise 182.70.xx.yy:5060.
How to advertise RTP ports?
Kamailio+RTPengine on a Centos s/m with a priv ip - 192.168.1.x
Asterisk is on another CentOs s/m with a priv ip - 192.168.1.y
pfsense on pub ip - 182.75.xx.yy 
PORT FORWARDING on pfsense-
sip and rtp ports to kamailio+rtpengine server 192.168.1.x.
How to make RTPengine listen on public interface-- 182.75.181.70?

sip.conf
========

[general]
context=external
realm=192.168.1.y

bindaddr=0.0.0.0:5080                
tcpenable=no                 
allowoverlap=no                         
transport=udp,wss,ws                    
srvlookup=yes                             
qualify=yes
directmedia=no
canreinvite=no
;---------NAT SUPPORT---------

externip=182.75.xx.yy
localnet=192.168.1.0/255.255.255.0
nat=yes
;nat=no               //tried but no RTP
;nat=force_rport,comedia      //tried but no RTP

;-----------RTP SUPPORT----------------
rtpkeepalive=30
disallow=all
allow=gsm
allow=ulaw
allow=opus
allow=alaw
allow=g723
==================
and i am using asterisk realtime support for mysql to store peer details.

With Regards,
Arish Haque