[SR-Users] Nat problems

Andrew Pogrebennyk apogrebennyk at sipwise.com
Fri Sep 2 21:24:43 CEST 2011

On 09/02/2011 08:58 PM, David Zambrano wrote:
> After doing some traces
> on the network I realized that the transcoder is trying to reach the
> router in front of the softphone and skipping the Kamailio
> loadbalancer. The call never reaches the softphone so the phonecall
> never completes. In UDP exactly the same thing happens, the call skips
> the Kamailio loadbalancer but the call completes perfectly fine.

Well, you can not open the TCP connection to the client behind NAT. You 
need to reuse the existing connection created during registration, so 
the request should go via load balancer by record-route or path. I'm not 
sure why this works for UDP, probably your router is too permissive in 
this case :-)

Regarding the loadbalancing and failover, I don't understand what is the 
problem. Could you specify which lb module do you use and preferable 
post the part of config responsible for failover. I believe you don't 
need to send request to both transcoders. To skip the transcoder that 
goes down you need to setup ping checks, if that is the only problem.

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