Netgear RT311 User Manual download pdf (Page 134)

Reference Guide for the Model FR314 Cable/DSL Firewall Router

B-8 Network and Routing Basics

Single IP Address Operation Using NAT

In the past, if multiple PCs on a LAN needed to access the Internet simultaneously, you had to

obtain a range of IP addresses from the ISP. This type of Internet account is more costly than a

single-address account typically used by a single user with a modem, rather than a router. The

FR314 firewall router employs an address-sharing method called Network Address Translation

(NAT). This method allows several networked PCs to share an Internet account using only a single

IP address, which may be statically or dynamically assigned by your ISP.

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.

Figure B-3. Single IP Address Operation Using NAT

7786EA

192.168.0.2

192.168.0.3

192.168.0.4

192.168.0.5

192.168.0.1 172.21.15.105

Private IP addresses

assigned by user

Internet

IP addresses

assigned by ISP

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Netgear RT311 User Manual Page 134