Two subnets public IP

Hello,
I’ve this situation:

Routerboard 1
P2P from my fiber ISP
eth1 IP A.A.A.B gateway A.A.A.A
eth2 IP B.B.B.B (this IP is part of subnet /28 that my ISP has given me)

Routerboard 2,3,4, … etc.
eth1 (WAN) B.B.B.C gateway B.B.B.B
eth2 (LAN) PPPOE, NAT, etc.

It’s all ok, and I can make also 1:1 nat in Routerboard 2,3, etc

Now my ISP has given me another C.C.C.X /29 subnet, routed on the same P2P.

How I must use this subnet on Routerboard 2,3, etc., where gateway is B.B.B.B, for 1:1 NAT?

Thanks.

Up, thanks!

any suggestion?

Up, please.

Anyone?