Private Ip Addresses; Single Ip Address Operation Using Nat - NETGEAR RT338 Reference Manual

Reference Guide for the Model RT338 ISDN Router
NETGEAR strongly advises that all hosts on a LAN segment use the same netmask for the
following reasons:
• 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.
• Local routers or bridges can determine which addresses are local or remote

Private IP Addresses

If your networks are isolated from the Internet (for example, only between your two branch
offices), you can assign any IP addresses to the hosts without problems. However, the IANA has
reserved the following three blocks of IP addresses specifically for private networks:
10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255
NETGEAR recommends that you choose your private network number from this range.
The DHCP server of the Model RT338 router is preconfigured to automatically assign private
addresses.
Regardless of your particular situation, do not create an arbitrary IP address; always follow the
guidelines explained here. For more information about address assignment, refer to RFC 1597,
Address Allocation for Private Internets, and RFC 1466, Guidelines for Management of IP
Address Space.

Single IP Address Operation Using NAT

In the past, if you needed multiple PCs on a LAN to access the Internet simultaneously, you would
have to obtain a range of IP addresses from the Internet service provider (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 Model RT338 router employs an address-sharing method called
Network Address Translation (NAT). This method lets several networked PCs share an Internet
account using only a single IP address, which may be statically or dynamically assigned by your
ISP.
1-12 Introduction