A note about NAT

Network address translation (NAT) substitutes a client's TCP/IP address with that of the NAT router, entering the substitution in a table, and making certain changes to the packet, including the IP address and TCP checksums. To external Web sites, it appears as if your entire subnet is one computer. While NAT is an excellent way to isolate your network from external users, NAT is incomplete as a firewall. By itself, NAT doesn't control packets to the same extent as full-fledged firewalls, which combine subnet isolation with packet inspection designed to monitor and control each packet based on its origin, destination, source application and content. Nevertheless, NAT remains a strong barrier against unwanted intrusions.

Janss is the president of Jansys Information Systems, a consulting firm that specializes in IS technologies for small businesses. He can be reached at bizcom@jansys.com.

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