Node in NAT mode

I'm building up the equipment for a new TEST case. Im trying to test, a case that the node sits on a LAN subnet that is not manged by the Node, but rather another network switch. Ive set the nodes lan settings too NAT and given it a 192.168.3.69 address.... Ive reaching out for help, the help document is a little confusing,.. I don't think all the settings needed to configure this properly exist on the configure page. The first atempt was to configure the node (hAP) with a 192.168.3.69 then after a reboot with the new settings. I can reach the node, but once I plug the 192.168.3.0 network into one of the LAN ports on the hAP, and a Rpi (with an established SSH connection) in to another LAN port on the hAP. The node becomes unreachable from the mesh after the previous connection is made. The Rpi is reachable from the 192.168.3.0 network, and the Node (hAP) as well. The node becomes unreachable from the mesh??? restoring the cables doesn't restore the previous state, that requires a reboot.  

What am I missing or is the gui missing something? 

"The other LAN Mode is NAT, which stands for Network Address Translation. In this mode the LAN is isolated from the mesh and all outgoing traffic has its source address modified to be the Mesh RF IP address of the node. This is the same way that most home routers use an ISP Internet connection, and all services provided by computers on the LAN can only be accessed through port forwarding rules. A single DMZ server can be set up to accept all incoming traffic that is not already handled by other rules or by the node itself. See Port Forwarding below for additional information."