NETGEAR DG814 DSL manual The following figure illustrates a single IP address operation

Reference Manual for the Model DG814 DSL Modem Internet Gateway

The router accomplishes this address sharing by translating the internal LAN IP addresses to a single address that is globally unique on the Internet. The internal LAN IP addresses can be either private addresses or registered addresses. For more information about IP address translation, refer to RFC 1631, The IP Network Address Translator (NAT).

The following figure illustrates a single IP address operation.

192.168.0.2

192.168.0.3

Private IP addresses assigned by user

IP addresses assigned by ISP

192.168.0.1172.21.15.105

Internet

192.168.0.4

192.168.0.5

7786EA

Figure B-3. Single IP Address Operation Using NAT

This scheme offers the additional benefit of simple firewall-like protection because the internal LAN addresses are not available to the Internet through the translated connection. All incoming inquiries are filtered out by the router. This filtering can prevent intruders from probing your system. However, using port forwarding, you can allow one PC (for example, a Web server) on your local network to be accessible to outside users.

B-8 Networks and Routing Basics