When you want a DMZ on your AT&T U-verse, it will assign a public IP... If you have a need for a static LAN ip this can be a problem. My Wii Media Center uses IPs to stream my videos. Maybe it could use a name but still is weird.
The DMZ machine runs Debian. If you simply assign a 2nd IP to eth0 (ifconfig eth0:1 192.168.1.10) then the AT&T gateway updates its table and turns DMZ off. DMZplus only works on DHCP hosts...
Enter 'macvlan'. Is like a vlan, but with MAC address. So you can have a virtual ethernet with a different MAC. Here is how I setup /etc/network/interfaces (Make the 2nd number in the MAC a 2,4,6,or E to denote "locally administered MAC"):
auto eth0 iface eth0 inet dhcp auto dmz0 iface dmz0 inet dhcp pre-up ip link add link eth0 dev dmz0 address 02:10:75:2a:82:c1 type macvlan post-down ip link del dmz0