Calls on IAX trunk fail after 2 minutes

I’ve setup 2 Asterisk boxes (pbx in a flash) and configured an IAX trunk between them. We can make calls just fine except just after 2 minutes has elapsed the call just goes quiet and we can’t here anything. The logs show nothing until either of the parties hang up. It’s as regular as clockwork. Anyone know why the call is failing?

Thanks in advance.

I’d be suspicious of any firewalls, NAT gateways, routers, etc between your two servers.

You could try using a network packet sniffer, or a tool like tcpdump to work out if the Asterisk servers are sending data that isn’t reaching its destination, or if they have actually stopped sending.

I am suspicious of them but I feel it’s related to something Asterisk is doing as it’s so regular. Like Asterisk after 2:40 duration in a call is saying OK now I’m going to do something that breaks something else, maybe NAT or the router. if I could figure out what Asterisk is doing I could start diagnosing NAT or the router/firewall.

gilester, you were right. I setup 2 more IAX trunks into different systems and they performed flawlessly. I went back to the original and got the remote system to re-route through a different router and it worked just fine. The original combo that broke the call was a Draytek 110 adsl modem into a Draytek 2910 router. We changed to a Draytek 2800 adsl modem/router and it all worked fine.



You should set a static IP for the IAX devices (defeats the point having it behind a NAT).

If it’s a WAN IAX setup Static IP is the safest solution. Just speaking from experience.

If your asterisk boxes are behind the firewall and are on LAN they still should have a Static IP.

IAX is a direct route unlike SIP which is more dynamic but will always need a sip proxy or SER.

I completely agree, I don’t work on systems that don’t have static IPs. If a customer has an ISP with dynamic IP then I walk away unless they are willing to switch to a static IP.

Further testing here with the IAX trunk is proving very reliable and good quality.


IAX2 is the best protocol to use when servers are behind NAT as only one port needs to be forwarded.

[quote]If it’s a WAN IAX setup Static IP is the safest solution. Just speaking from experience.

Static IPs are always best but not always possible, Dyndns solves many problems and for SIP as long as you register to your ITSP then being a dynamic IP isnt to big an issue.

  • to * via sip will not need a proxy, even if both boxes are behind NAT portforwading will solve most rtp issues


Thanks for completely dissecting my answer :smiley:

But I’ve had exactly the same issue with some of my customers who decide they want multiple trunks (most of the time to the same box) and worst most of the time they had dynamic ips (root of problems)…they resell my services and numbers, but I wonder why they even bother with a dynamic subscriber line (not even a leased or transit)…they are doing it at home…

Just today I got absolute fed up saying we don’t offer that…without a static ip although we do recommend dyndns or dynip.

I have just configure openSips to handle all these issues no customers were affected with the adjustment and my asterisk cluster is now performing beautiful and the problematic ones have recently left feedback.

Nat issues (i.e multiple numbers same port etc) for IAX2 static ip very much recommended. Allows the guys at the helm to Qos and shape calls better. with the transversal there is quality to also take into account (that matters to me more)

Thanks Ian, I know your right and the reasonings are spot on.