WRS connection guide has also been developed over years of experience hosting up to 3 races a week, plus test sessions and 'beer rooms'. 👍
My router admin is pretty sweet, nicely designed with built-in port forward profile which I could assign visually to the PS3. Still NAT2 though.
I don't think you can actually get NAT1 if you use a router? In the diagram, it's direct to the modem with no router in between. Even if it's a combined router and modem single unit. In the diagram (and in the PS3 settings) you need physically connection directly to your modem, with no router, so you have to set your ISP account login details in the PS3 directly.
With my previous router and ISP, which didn't have full UPnP and didn't have a pre-made port forward profile, I gave the PS3 a fixed local IP and put that local IP in the DMZ. Essential, switching off the router's functions for the PS3 while keeping them for everything else - don't switch off your router firewall for everything else! That got me from NAT3 to NAT2 and made online lobbies 10x more reliable.
@JLBowler quotes the system SNAIL uses on the night, since there isn't time to diagnose network setups when 10+ people are ready to race and some of us have stayed up until 2:30am just to start the event! D3 finished after 5am for me February week 4.