[OpenSIPS-Users] fix_nated_sdp and rtpproxy

Bogdan-Andrei Iancu bogdan at opensips.org
Thu Nov 16 08:01:31 EST 2017

Hi Yury,

RTPproxy learns not only from SDP, but based on the incoming RTP 
traffic. Your Client will send RTP to RTPproxy (as the Client will 
receive back a valid IP in the SDP) and RTPproxy will see where the RTP 
traffic comes from and starts sending back RTP to that IP:port.

Just be sure you do not use the "a" and "r" flags when calling rtpproxy 


Bogdan-Andrei Iancu
   OpenSIPS Founder and Developer

On 11/16/2017 02:48 PM, Yury Kirsanov wrote:
> Hi Bogdan,
> Thanks for your answer and support! But the issue is that there is a 
> private IP address in SDP coming from the client so if I just pass it 
> via RTP proxy - it would learn that incorrect IP and would try to 
> forward packets to it causing one-way audio. That's why I first wanted 
> to overstamp that incorrect IP with received IP and then pass it to 
> the RTP Proxy. Hope this makes my idea clear.
> Regards,
> Yury.
> 2017-11-16 23:32 GMT+11:00 Bogdan-Andrei Iancu <bogdan at opensips.org 
> <mailto:bogdan at opensips.org>>:
>     Hi Yury,
>     Why do you need to update the incoming SDP before engaging
>     RTPproxy ? Just pass to it whatever you get into SDP (even if
>     private) and let rtpproxy to "learn" the correct IP:port of the
>     media end points based on the incoming traffic.
>     Regards,
>     Bogdan-Andrei Iancu
>        OpenSIPS Founder and Developer
>        http://www.opensips-solutions.com <http://www.opensips-solutions.com>
>     On 11/14/2017 04:05 AM, Yury Kirsanov wrote:
>>     Hi,
>>     I have a problem with remote client who can't properly configure
>>     NAT and is sending private IP in all SDP and SIP packets. I've
>>     resolved issues with registration but can't resolve the issue
>>     with SDP. My topology is as following:
>>     <Client> ----- <NAT router> ------- <RTP Proxy> ----------
>>     <OpenSIPS> -------- <NAT> ----------- <PBX>
>>     So, I need to simultaneously engage RTP Proxy to bridge external
>>     Internet and our local LAN and need to rewrite SDP body of
>>     original Client's packet with received IP address. If I'm doing
>>     fix_nated_sdp and then rtpproxy_offer - I'm getting doubled IPs
>>     in SDP message, like this:
>>     Is there any way to update SDP of client's packet and then
>>     command RTP Proxy to use updated IP? Thanks!
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