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Hardware Manual for the Model CG814WG Wireless Cable Modem Gateway
Networks, Routing, and Firewall Basics D-7
NETGEAR strongly recommends that you configure all hosts on a LAN segment to use the same
netmask for the following reasons:
• So that hosts recognize local IP broadcast packets
When a device broadcasts to its segment neighbors, it uses a destination address of the local
network address with all ones for the host address. In order for this scheme to work, all devices
on the segment must agree on which bits comprise the host address.
• So that a local router or bridge recognizes which addresses are local and which are remote
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
CG814WG Gateway 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.
255.255.255.0 /24
255.255.255.128 /25
255.255.255.192 /26
255.255.255.224 /27
255.255.255.240 /28
255.255.255.248 /29
255.255.255.252 /30
255.255.255.254 /31
255.255.255.255 /32
Table D-2. Netmask Formats