Port forward from one WAN?

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Hi! Is it possible to port-forward from one WAN?

I have a DSL connection that’s somewhat flaky, and an LTE modem providing redundancy. I have tailscale, but would like to just be able to access the system via the mostly-up DSL connection as well.

I’m guessing easy option would be to listen on multiple interfaces/IPs and set up split tunneling on that second interface. Curious if there’s any other options native options.

Right now, my setup actually has another router behind SmoothWan, so the split tunneling doesn’t really work for me (but could if I reworked my network).

Edit: Seem to have gotten it working.

For some debugging history - I used tcpdump with various options to confirm that packets were leaving Smoothwan to my downstream router, and coming back with a repsonse from the router. From there, I had to figure out how to get tracing working - it was relatively simple, except that logread isn’t the tool to see them - use nft monitor trace. From here, I could see that the responses were going out via connectify0, which wont work. But I saw stuff about PBR in the traces, so I tried adding a PBR with just “local port” only set, and it seems to work.

tl;dr

  1. Add a regular old port forward
  2. Add a PBR with the same local IP / port to the interface of your choice.

I’m not sure if there are any downsides to the approach I took.

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Hi! Yes that sounds right, glad it works, you could also use IP rules instead of PBR in case it gives you problems: Bypass clients to a specific WAN - SmoothWAN
You can also add additional firewall zone similar to WAN to ensure that the port forwarding rule does not apply to other unwanted interfaces.