Incoming calls dropping after 6 seconds (no ack to 200 OK)

Hi,

I am trying to set up an Asterisk installation (FreePBX), but I’m having some troubles receiving calls (outbound calls are ok). I’m trying to debug the issue using sngrep, and this is what I see for an incoming call:

Basically the call seems to work for about 6 seconds, then it is dropped. Looking at the packet capture, there is no ACK for the 200 OK packet sent by the callee after answering to the call. This may indicate a problem with the NAT settings, but I already set up port forwarding for port 5060 (SIP) and 50000-65000 (RTP).

The IP address in the Contact field is correct.

Does anybody have some ideas?

There are three addresses associated with the source: medial, source, and some intermediate proxy.

Having said that, it seems to handle your media address correctly, so I can’t think why it cant handle your contact address, unless maybe some firewall somewhere only opens on INVITEs and thinks it it is different session, because the ACK is coming directly.