[asterisk-dev] IAX2 call leg optimization behind firewall

Wolfgang Pichler wpichler at yosd.at
Mon Sep 20 02:14:10 CDT 2010


hi all,

i am trying to get call leg optimization working on the following scenario

PSTN -> server A -> calls server B -> server B calls server A -> PSTN

So in a perfect world - asterisk will optimize server B out of the path -
and it does try so - but fails

server A is in a private network behind a firewall
server B is in a private network behind a firewall

the firewalls are configured to forward port 4569 to the internal machine


So
- Server B is sending TXREQ to server A for both call legs (with the public
ip of server a as destination ip)
- Server A receives the TXREQ
- Server A does send TXCNT to public ip server A - firewall does forward
packet to server A
- Server A deos receive TXCNT - but packet is coming back from the firewall
with source address of the internal ip of the firewall - and not the public
ip - so i think asterisk will ignore it

and so the call leg optimization will fail

I have done a test setup without the firewalls in a local network - there
the given scenario does work perfectly fine.

So - is it correct - that when the firewall would return the packet with the
public ip the cal leg optimization would work ?

best regards,
Wolfgang
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