How to setup PPPoE on a new interface/WAN

[mcon]

I currently have a three interfaces setup: standard LAN+WAN+DMZ.
WAN is connected to a modem/router doing actual NAT and presenting itself to OPNsense as 192.168.1.1
This is working and I can do what I need.

Now I get a second line with much the same modem, but I should connect it in PPPoE on another Interface.
This second modem is supposed to give me a static public routable IPv4.

I tried setting it up, but I don't see any activity in the logs, so I must have missed some relevant setting.
Can someone tell me exactly what are the steps to setup a second WAN using PPPoE?
I was unable to find relevant documentation.
Notice I would like to avoid disrupting the currently working setup (which I'm using to write this, among other things).

Many Thanks in Advance
Mauro

[cookiemonster]

Interface setup: https://docs.opnsense.org/manual/interfaces.html
The section "IPv4 Configuration type" is where you select PPoE.
When adding a second WAN you are going "multiwan": https://docs.opnsense.org/manual/how-tos/multiwan.html
Save your config frequently and have a medium like a USB stick available so you can restore after reboot if you get in a pickle.
I suggest drawing for yourself a diagram with IP ranges beforehand and which device will be doing which services so you don't get conflicts.

[mcon]

Thanks @cookiemonster,
unfortunately I blocked much earlier than that.

Before switching to PPPoE I tried a multiWAN using plain ISP modem/router.

I have the (perhaps unusual) situation where my two uplinks are both crippled in different ways.

GW1 is quite fast fiber, but has a "dynamic IP" (i.e.: my external IP changes every now and then, so it's uncomfortable way to get into my LAN/DMZ.

GW2 is slower ADSL, but has a guaranteed fixed IP I associated with my domain.

Situation is similar to [this question](https://forum.opnsense.org/index.php?topic=21158.0) and is not covered in `MultWAN` docs which seem to deal mainly with failover/load-balancing which I don't really need.

To recap:
- I am fine with a single outgoing GW (GW1)
- I need Port forwarding from both GW1 and GW2 (80, 443) to a single server on DMZ (`nginx` reverse proxy)
- problem is responses to packet coming from GW2 are sent back through GW1
- I have all rules in Firewall: Rules: BKP and Firewall: Rules: WAN with no explicit `Gateway`
- such rules seem not editable and I didn't find a way to force GW2 on BKP

General network diagram is:


I am obviously missing something, but I can't understand what.
I can provide the full (current) config if useful.

Many Thanks in Advance

[cookiemonster]

On this one I am not sure. I think we can only have one default gateway and that's why the traffic goes back on it even when the incoming connection was from the other. There is a "reply to" and choice of gateway options (exposed on "advanced features) but only per interface. Maybe a play here but as I say, I am not sure if it can be setup to do what you need.
Or maybe with an tag set in the NAT port forward and then a match on it with those reply options on the filter rule on the settings above.
Sorry, really can't say.