Please let me know how you managed to achieve this, Ranger Home!?!

I spent hours with the prior model AT$T router [with similar UI] attempting the DMZ mode approach and could not get it to work. It seemed to "forget" that setting after every reboot and then the whole network would crash with IP address conflicts. I finally gave up and just used the AT$T router.

Can you point me to a definitive "how to...?"