I need it to connect to my home network wirelessly (wireless WAN - upstream). This is a bridge to a little "lab" setup - a Raspberry Pi Cluster. So that sounds like a Bridge or Client or Repeater or Extender of some sort. I can set a Static IP of 192.168.1.2 that my home mesh router assigns to it.
However, I also want it to be a DHCP server downstream to the lap, on a seperate Class C. I don't see that this allows a DHCP Pool with a different IP space, say 10.0.0.20-40. That sounds more like I want it to be an Access Point but wireless WAN. Which it doesn't seem to allow.
Any way to do this? If not natively, would OpenWRT firmware allow it?
There is "Repeater" connectivity for Wireless WAN (uplink via wifi)
There is network mode "router" for having a separate LAN subnet with it's own DHCP server, and it's own IP subnet. The "router mode" will use NAT and will use the firewall. All connections will use the WAN side (wifi with repeater) IP address.
The connections initiated from the LAN side to the WAN (wifi) side will work. The answers (reverse direction) over these initiated connections will also work.
NAT and firewall prevent reverse initiated connections (from the WAN wifi to the local LAN) unless the connection is already specified in either the "port forwarding" or the "DMZ host" setting. The LAN side combines all the home wifi networks (not the guest wifi), and the LAN ethernet ports as physical networks for the local LAN subnet.