Reference Manual for the Model DG824M Wireless ADSL Modem Gateway
B-8 Network and Routing Basics
In the past, if multiple PCs on a LAN needed to ac cess 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
DG824M gateway employs an address-sharing method called Network Address Translation
(NAT). This method allows several networked PCs to share an Inte rnet account using only a sing le
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 tran slation, refer
to RFC 1631, The IP Network Address Translator (NAT).
The following figure illustrates a single IP address operation.
Figure 7-3: Single IP Address Operation Using NAT
7786EA
1
92.168.0.2
1
92.168.0.3
1
92.168.0.4
1
92.168.0.5
192.168.0.1 172.21.15.105
Private IP addresses
assigned by user
Internet
IP addresses
assigned by ISP