u can use the modem u already have, u simply set eth00 to b ur local network, then setup an internet connection, i am used to adsl so in my setup –> network i have eth00, eth01,ppp0 eth01 is linked to ppp0. ZS will do all your DHCP w/ minor setup, routing, firewalling.the NAT will work “out of the box” under adsl the NAT auto sets itself.