Seems trivial, but the number one source of problems is a misconfigured firewall. Misconfigured for the purpose of allowing FreeSWITCH network traffic to flow, that's it. But maybe the person in charge of maintaining the firewall rules is unaware of what kind of traffic (addresses, protocols, ports) FreeSWITCH will generate and need.

When investigating a problem, a one way communication, calls dropped after 30 seconds or a minute, all those kind of failures, first be sure the traffic is not blocked.

Open all ports and all protocols on your FreeSWITCH server machine (eg, disable the server firewall completely). Edit the file /usr/local/bin/disable_iptable.sh to be:

#!/bin/sh 
echo "Flushing iptables rules..." 
sleep 1 
iptables -F 
iptables -X 
iptables -t nat -F 
iptables -t nat -X 
iptables -t mangle -F 
iptables -t mangle -X 
iptables -P INPUT ACCEPT 
iptables -P FORWARD ACCEPT 
iptables -P OUTPUT ACCEPT 

Then make it executable, and execute it (DO NOT EXECUTE IT LINE BY LINE! You'll risk to be locked out from your server):

chmod +x /usr/local/bin/disable_iptable.sh 
/usr/local/bin/disable_iptable.sh 

Now restart FreeSWITCH, and see if the problem is still there. If no joy, check also the following list:

• If behind NAT
  • what is the public address of FreeSWITCH? Is correctly reported into all ext-rtp-ip and ext-sip-ip parameters? (go to /usr/local/freeswitch/conf and execute "grep -r ext-")
  • are all the port and protocols "open" and forwarded from the Internet to FreeSWITCH?
• If an external firewall, worst of all an appliance
  • is it blocking your traffic?
  • worst, is it applying some sort of ALG (Application Level Gateway) to SIP or other protocols? You DO NOT WANT ANY SMARTNESS in your router or firewall. They're not smart enough to be smart, and they end up doing subtle and intermittent damages. Believe. Disable all kind of smartnesses in routers and firewalls