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!