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In the SIP Settings module in FreePBX, make sure that you have defined these IP addresses:
The external IP address that your trunks or extensions are connecting to
The internal IP subnet that is set up
You also need to make sure you bind asterisk to the floating IP address in the SIP Settings module.
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Ports
Make sure you have ports 5060 and 10000-20000 UDP opened on your firewall, pointing to the floating IP address.
Make sure all SIP ALG and SIP Helpers are disabled on the firewall.
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