[SR-Users] NAT Traversal

[Spinov Evgeniy]

May be I miss some important details? No suggestions?

Thank you.

> Hello, all.

> Using nathelper + rtpproxy for subj. Kamailio has public and private
> network interfaces. Asterisk is only private. RTP Proxy is working in
> bridge mode and relaying traffic from UAC to Asterisks.

> Everything is working fine, except one configuration. When the client is
> behind router ( a specific one, I do not have an access there to
> check ), and this UAC is making a call to other public extension, which
> is behind router, then RTP Proxy is relaying traffic to the caller,
> using another UDP port, then the packets arrive.

> For instance: 
> UAC 1 -> UAC 2

> PUBLIC_IP:10 > KAMAILIO_IP:5555
> KAMAILIO_IP:5678 > PUBLIC_IP:12

> While for the UAC 2 it looks like:

> PUBLIC_IP:20 > KAMAILIO_IP:6767
> KAMAILIO_IP:4564 > PUBLIC_IP:20

> The source and destination UDP ports are the same. As result, I can hear
> UAC 1 and he cannot hear me. 

> In case of we have UAC 3, which is behind other router, call is working
> fine with same configuration.

> "It's routers fault" you can say, but in the same configuration ( I mean
> network, not kamailio ) it worked, but when RTPProxy was not in bridge
> mode and Kamailio and Asterisks were in public network. Reinvites are
> not allowed in both cases. 

> The question is, why the source and destination UDP ports are different?
> Using STUN in first case, cause without it, private IP written in
> contacts and as result, traffic relayed from Kamailio is incorrect,
> cause heading to private network which is unreachable.

> Any ideas where to dig?