Appointed adress ip when in dmz i have just one server

[henze]

hello,
i i have 4 dmz . For 2 dmz i had 2 servers so it should have adress ip appointed. in my configuration i use DHCP static and i give a range . I work widh virtual machine  so every time when i start to work the ip change ! so how can i fixe it ? should i disable DHCP or what ?
thanks to answer me !