Private Ip Addresses; Single Ip Address Operation Using Nat - NETGEAR RT311 Reference Manual

Reference Guide for the Model RT311 and RT314 Internet Access Gateway Routers
NETGEAR strongly advises that all hosts on a LAN segment 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

Private IP Addresses

If your local network is isolated from the Internet (for example, when using NAT), 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 RT311 and RT314 routers 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 multiple PCs on a LAN needed to access the Internet simultaneously, you would
need 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 Model RT311 and RT314 routers employ 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 Internet service
provider (ISP).
Networks and Routing Basics 10-7