Private ip addresses, Single ip address operation using nat – NETGEAR ME103 User Manual

Page 89

background image

Reference Manual for the ME103 802.11b ProSafe Wireless Access Point

Network, Routing, Firewall, and Cabling Basics


August 2003

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: - - -

Choose your private network number from this range. The DHCP server of the ME103 Access
Point 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
. The Internet Engineering Task Force (IETF) publishes RFCs on its Web site at

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
ME103 Access Point 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).