Gateway monitoring not working

[Szymon]

Re: Gateway monitoring not working post-2.3 upgrade? Read here

Hi I'm new to pfsense and would need some help.
I've tried all recommended in topic related to monitoring post 2.3.

Netgate SG-3100 running
2.4.4-RELEASE-p1 (arm)
built on Thu Nov 29 14:06:34 EST 2018
FreeBSD 11.2-RELEASE-p4

My setup is BT openreach modem >> pfSense (WAN port - IPv4 PPPoE, IPv6 DHCP6) >> ...
gateway WAN_PPPOE (default) interface: WAN | Address Family: IPv4 | Gateway: dynamic

For a some reason my GW IP is reported as Offline.
In System >Routing Gateway and Monitor are showing IP 172.x.x.x
My WAN IP is 86.x.x.x

Can anyone help/explain what is happening and how to fix GW reporting?

[Grimson]

https://www.netgate.com/docs/pfsense/book/routing/gateway-settings.html#monitor-ip RTFM

[Szymon]

Thank you. I still don't understand where 172.x.x.x (private IP) is coming from? as it was set to default, why default is not picking up WAN IP?

I've left Gateway as dynamic (it still displays 172.x.x.x address), but I've added Monitor IP 8.8.8.8 (Google DNS).
I'm not sure if this is correct, but I can see now correct status in Status>Gateways