My main router/AP is a Netgear Nighthawk R7000 (Broadcom) which, after experimenting with various alternative firmwares, is back on the Netgear official FW.
I've got an ethernet-only security camera that I want to place inconveniently far from the R7000, so am hoping to use my TP-Link TL-WR842ND (Atheros) which is currently running OpenWRT 22.03, as some kind of repeater or bridge ... I don't know the right terminology, but the TP-Link would connect wirelessly to the AP and would have an ethernet connection to the security camera.
I gather that I can't use the WDS method because that would require both devices to be on OpenWRT. Do I need to use the relayd method? I've seen passing remarks about a variety of other approaches. What would be recommended as reliable for my equipment, and relatively straightforward to configure?
You could relayd as you mentioned or connect to the wireless in WWAN config and forward the needed ports to the camera.
Relayd would keep the same LAN and IP scheme.
The most standards-compliant way to do this is a routed client with symmetric routing (not NAT).
The camera(s) beyond the repeater will be on a separate subnet from the main house LAN. You will need to be able to install a static route in the house main router to the camera LAN using the repeater router as a gateway. Connecting to a camera from the house LAN is possible, but you will need to manually enter its IP on the camera network into the viewing software-- applications that probe for cameras usually won't work between LANs.
Once this is set up though it will be very fast and reliable. The cameras will have full access to the Internet unless you choose to firewall them off.
Hmm, I think I follow that, and yes I can configure a static route with the repeater as gateway. The OpenWRT guide is pretty confusing (compared to the relayd guide, which is very easy to follow) ... I'll read it over a few times and see if I can figure out what it's saying.