I am using the Kamailio 4.1.2 with RTPProxy 1.2.1 as a SIP Proxy. I want to ensure that all my sip and media (RTP) passes through the SIP Proxy (Kamailio + RTP Proxy) while we my SIP Client sends any SIP and RTP to SIP Server (asterisk). So it is like below:

SIP Agent <--------SIP+RTP---------->SIP Proxy(Kamailio+RTPProxy)<------SIP+RTP-------->SIP Server(Asterisk).

Now it is working fine with my current configuration on Kamailio with RTPProxy with SIP and RTP both if my SIP Agent is on the 802.11 LAN that is my PC have local IP address like 192.168.1.2.

Now I am facing the problem in the case where my PC is accessing the internet through the USB data card (or Internet USB dongle). Here my PC IP is like 116.203.51.209. In this case my SIP is successfully passes through the SIP Proxy and works good. But in this case my RTP is does not passes through the SIP Proxy (RTPProxy). The SIP Proxy(Kamailio + RTPPRoxy) and SIP Server is running on the public IP.

Please find attached my kamailio.cfg.

Please let me know what is the issue.

Thanks and Regards