[asterisk-users] double NAT - one way audio

Andre Gronwald andregronwald78 at gmail.com
Sat Mar 11 10:50:00 CST 2017

Hi all,

I have a setup which is not working right now:

Provider - DSL-Router ( - Bintec-Router ( - 
Asterisk (

My issue: Everything works, but RTP is only going from my Asterisk 
towards the provider. Asterisk is configured to use SIP-ports 55060 and 
RTP-ports 51000-51999.
Those ports are forwarded on DSL-router  to the bintec router and from 
the bintec router to asterisk.

what I see is the Invite from provider goes to and rtp port 
7070. my asterisk responds with audio to be sent to ip address port 51242.
Afterwards RTP goes from to but the 
RTP back is not coming in.

I would expect the RTP traffic to be sent to (intetnal port 51242 - then i would have successfully two way audio.
But why is port 7070 used?

The DSL-router is a speedport w724v type A.


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