IAX 2 - Different address for uplink than downlink

I have 2 asterisk servers, 1 in a foreign country.

I think that my ISP in the foreign country has configured their network in a way such that incoming traffic comes through one interface, while outgoing goes through another? I am not certain if this is the case but I think that they want to conserver bandwidth usage for one of their links, thus using it only for downloading, while uploading goes through another.

On my home asterisk server, running on Fedora Core 6, I have opened up the remote IP so that the 2 servers can talk to each other using IAX2 on port 4569.

However, when I do a tcpdump I see packets going to my remote asterisk server, but the return packets appear to be from a different IP address. Can I somehow configure Asterisk to handle this?


if your asterisk server is being nat’ed, i don’t see how. maybe some kind of vpn tunnel?

Hi Hovik,

please read my thread from 23 of Dec " 2 Asterisk server Germany - Saudi Arabia IAX2 connection "

Have we got the same problem?


I don’t think so.

it’s entirely possible they are using different routes for traffic in different directions. this can create odd issues, like latency one way is different from latency the other way.

however in general traffic should come FROM the same place you send it TO.

I agree that it’s probably a NAT problem- possibly somewhere on the other side there is a multi-homed network that is not matching up interfaces correctly. or maybe an * box running a really old version that doens’t correctly deal with multiple network interfaces, or broken routing in such a way that packets are going out the wrong interface. either way it shouldn’t happen. Asterisk can’t (that I know of) deal with a response coming from a separate IP than the query was sent to, just about nothing can because it is very hard to match the two up.

hope that helsp