Help with pppoe-server

Installing and Using OpenWrt
1

Dear all,

I have a spare ISP router (zyxel) and a couple of OpenWRT devices in 2 separate homes.
I currently use the OpenWRT devices as main and both are interconnected using a layer2 bridge with zerotier.
I do manage to use the spare ISP router as a dumb AP with DHCP disabled and use its DLNA/SMB server capabilities in my whole network.

The "issue" is that I wanted to free one lan port and use the dedicated WAN port of the dumb AP instead.
I started by setting up a rp-pppoe-server with the proper VLAN and it kind of worked after a few tries. But there is no communication between the LANs ( as expected).
I've tried to tweak both the pppoe-server and the ISP router ( can only perform some minimal adjustments) to try to "enable" the Public-LAN feature that the ISP router is supposed to have ( https://service-provider.zyxel.com/compact-help/AX-DX-EE-EX-PX-Series/index.html#page/AX-DX-EE-EX-PX_5-70/h_NetworkSetting_HomeNetworking_LoopGuard.html#ww1710860 view LAN Additional subset ), to avoid having multiple NATs on my internal network, but I cannot make it work.
It's just a networking exercise, but it's kind of driving me mad not being able to do it.

Does anybody have a similar setup and manage to make it work ?

Best regards

2

This approach does not make sense, PPPoE is rather CPU intensive, so performance will be 'really bad', worse than 'just' losing the useless WAN port (and I really don't want to think about Public-LAN via PPPoE(-server)…).

While it is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail, doing so in this case is just wrong.

3

Dear slh,

Thank you for your opinion, but I disagree on the hammer/nail part.
It's not like I want to use PPPoE, but rather that the ISP router WAN port is "locked" in that mode.
I've tried to use other protocols and configurations, but none worked.
There is no custom firmware for that router nor the root/admin passwords are public, so I'm stuck with a limited number of configuration options.
Even the pppoe part is limited, since it's the default configuration of the port when doing a factory reset.

Best regards.