If you are using DNS on your internal network, the best option is this: 1.- Configure the IP of your ISP DNS as your DNS forwarder (IP Properties of your DNS server). 2.- Configure your DHCP Server to assing the DNS option with the IP of your internal DNS. This allow local name resolution. 3.- Configure external interface of ISA Server witn NOT DNS IP. Configure internal interface with your internal DNS as the primary DNS. Configure the second DNS with the IP of your ISP. 4.- Configure lat and ldt tables on ISA server (ISA Console -> Server -> Network) with your internal IP range and your internal domains. 4.- Your SecureNAT, Firewall and WebProxy clients will use your internal DNS to resolve local and internet names. Internet names will be resolved throug Forwader DNS (ISP). Regards.