DMZ does not seem to work with XMG3512-B10A

simple

I'm trying to expose my Asus RT-AC87U router but DMZ does not seem to work. My Asus router is still reporting my LAN IP: 192.168.200.2. 

Also tried port forwarding ports 443 and 80 but that doesn't seem to work either. 

Any help appreciated. 

#Others_June