Openwrt to Passthrough the public ip received by pppoe

Installing and Using OpenWrt
1

hello,
i want my openwrt to passthrough the pppoe ip to a watchguard firewall device.

is this possible ?

so far i have a D-Link DAP-X1860 with OpenWrt 23.05.5 , a vdsl modem with 2 ethernet switch ports. pppoe connection on OpenWrt 23.05.5 runs fine.
with NAT , the watchguard is getting a privat ip via dhcp and can access internet.
i tried to leave static ip of openwrt lan empty and disabled Masquerading
but the pppoe ipv4 is not offered to watchguard.

chatgpt said it would work this way.
is Passthrough of pppoe ip even possible ?

2

Then let chatty explain, how, I'm curious and all ears...

What do you even want to achieve and btw, there is no "IP passthrough".

You have multiple options.

  1. Public and Private IP on OpenWrt with NAT, and your watchguard is doing NAT to.
  2. Set static routes between OpenWrt and watchguard, and doing NAT only on OpenWrt
  3. Use IPv6 and just use routing.
  4. Can't your watchguard do PPPoE, why do you have the watchguard behind OpenWrt anyway?
  5. Even more broken NAT scenario: Doing 1:1 NAT on OpenWrt and Masquerade on watchguard!

PS: Someone should jump in and tell me again how much more easy and simple IPv4 is!