Встроенный сервер DHCP на Windows XP:

netsh routing ip autodhcp uninstall
netsh routing ip autodhcp install
netsh routing ip autodhcp set global 192.168.100.0 255.255.255.0
netsh routing ip autodhcp set interface name="int" mode=enable
netsh routing ip autodhcp set interface name="ext" mode=disable
 
netsh routing ip autodhcp add exclusion 192.168.100.250
netsh routing ip autodhcp show interface name="int"

http://manaeff.ru/forum/viewtopic.php?f=3&t=886