What service for DynDNS when pfSense is behind another router

[dhjdhj]

I have a dynamic IP address and want to use a service like DynDNS but running it on my pfSense box.
However, that box is behind a Verizon FIOS router and so the WAN address of my pfSense box is in fact just a local address on the 192.168/1/24 subnet. As far as I can tell, the pfSense box wants to monitor that WAN address rather than using something like "whatismyipaddress.com"

How can I configure my pfSense so that it can figure out the real external IP address of my network for use with DynDNS?

Thanks

[javcasta]

Maybe this video help you.

Setting up Domain Name (Dynamic DNS) for Verizon Fios Router :
Youtube Video