I saw in a thread a recommendation to use a DDNS service for remote extensions on dynamic IPs and whitelist their FQDN. The last I knew, IPTables didn't take FQDNs. Does this work and if so, how?
Do it in your router.
With FreePBX firewall and responsive enabled you don't need to whitelist remote phones.
I was researching the Responsive firewall when I came across the threads saying to do the whitelisting as the "new" feature was looking to be less accurate than originally proclaimed.
Huh. It's fully accurate.
The responsive firewall is one layer of protection. Whitelisting IPs/fqdns is another.