Firewall DDNS hostname updating

Perhaps I missed it, but is there any info / docs on how the DDNS works if you enter a hostname for a network rather than an IP or subnet?

How often is it updated?

Are there any options / configuration for the frequency?

How is it updated? Cron?

Thank you.


Seems to me the DDNS refresh rate is 15 minutes and I think it’s hard-core into the package FreePBX uses. The system will validate the address through DNS WHENEVER there’s activity outside the network, so a good, responsive DNS is a must.