"Unusual" ISP setup, how to get it to work with CARP?

[marama]

Hi there!

Setup:
ISP => cable modem (bridge) => pfSense (DHCP & Static) => servers

I don't know the name of the setup, so I call it "unusual". My ISP told me I get 4 static IPs (213.47.xxx.20-24), so I've created the 4 IPs as virtual IPs (alias) and I set them in NAT and Rules.

My pfSense WAN interface pulls the IP with DHCP and status shows this.
IPv4 Address
213.47.xxx.xxx
Subnet mask IPv4
255.255.255.248
Gateway IPv4
212.186.xxx.xxx (this can change)
(please note that gateway is in different subnet then the DHCP IP!)

Everything works, except I cannot get CARP to deal with this because if I try to assign a static IP (one of the 4 IPs) and if I try to enter the gateway from the other subnet, I get an error.
So it's a DHCP with static IP behind it. I've tried to have the same setup on the secondary, but the ISP bridge setup doesn't support 2 DHCP clients.

Any idea how I can deal with his?

TIA