I have two networks, one lan and one iot. I would like to be able to stay on lan with my device and print without needing to connect the device to iot network, reason being that iot devices like printers don't need wan access.
lan forwards to iot and wan (with input accept, output accept, forward accept).
iot doesn't forward anywhere (with inut accept, output accept, forward reject).
This should be enough as I understand, but I looked around and found this: Help with routing guest to printer and based on that I tried to go to Traffic Rules and add:
Forwarded IPv4 From lan To iot, IP static-ip-for-printer-here Accept forward enabled, but still nothing.
Cups keeps complaining with No suitable destination host found by cups browsed if I don't connect my device to iot network.
I was trying the automatic detection. So I suppose that's why it fails, I'm choosing the printer which was discovered when I connect to iot network, but I'm connected to lan.
Will test to manually specify printers static IP. Seems I could also setup cups on OpenWRT.
Automatic detection relies on broadcasts, which routers typically do not propagate outside their respective subnets. This is by design. There are various hacks and workarounds, such as relay daemons, which may or may not be suitable for your needs.
This can get complicated real fast. Many printers with wireless can provide 2 interfaces.
Ad-hoc unencrypted typically labeled with the dumb-down description of "Guest". Print jobs go directly to the printer.
Infra-Structure and encrypted where the print job goes through the router.
If your router has a NIC ports, HP software will disable the printers wireless. Jobs go through the router unencrypted and with greater speed than wifi.
Based on the above, it would be helpful to know how your printer interfaces with the LAN. If you can, a static NIC should be the most reliable setup.