HI cao

You would need to take a look to SDPs on INVITE and ACK to check , external IP address are there in order to work properly. If that is the case, you would need to check that packets are forwarded internally behind two NATs.

What RTP Proxy are you using? I highly recommend to use rtpengine

Thats not a recommended situation we would not have when ipv6 would be a really. Hope to be soon! :)

Regards

2016-05-09 6:34 GMT+02:00 cao tao <csuappreciation@gmail.com>:

Hello:

     I use kamailio as my SIP signal proxy, and media-proxy as RTP relayer. It works well at many situations. But when it comes to two layer of NAT(a user behind two layer of NAT),  I got a single way media(the sip signal layer was ok). I can’t hear the voice of user who behinds two layer of NAT, but he can hear the voice of mine.

Most part of my kamailio config is default, and simply enable media-proxy by engage_media_proxy()：
        if (is_method("INVITE") && !has_totag()) {
engage_media_proxy();
        }

And in my UAC/UAS side, I use PJSIP.

Can anybody give me some help?

Any suggestion will be appreciated!

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