If its a private IP address then pfSense goes out to the web to get the public IP address.
That was the piece of "magic" I was trying to validate, as my searches didn't find anything that spelled it out.
Everything else, I already knew, as I've been running pfSense for quite a while now, with ZoneEdit handling the DNS for me.
@wallabybob:
If the public IP address changes more frequently than daily then it would be better if the IP address of the monitored interface changed more frequently OR if the address was polled more frequently.
I think my searches revealed that I could load the cron package, and change the frequency of the check.
The IP only changes very rarely, but on those odd occasions, waiting for a number of hours for the update could be quite frustrating.
Now all I have to check, is if either the FTP "helper" in pfSense when it has a "private" WAN IP, or the VoIp box, is smart enough to modify the passive FTP replies to use the public IP. I know that pfSense, when it has the public IP on the WAN interface copes quite happily.
Cheers.