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What is a NAT?Presently there are over 100 million servers and 350 million users on the Internet. In order for successful and efficient communication, each computer and server needs an IP (Internet Protocol) address. An IP address is a unique 32-bit number (IPv4) that identifies the location of a specific computer on the network. Mathematically, there can be up to 4,294,967,296 unique addresses (2^32), but in reality there are only 3.2 to 3.3 billion due to class separation, multicasting, testing, and other use. The size of the Internet is increasing exponentially and the rate of growth will soon exhaust the depleting resource. To delay the inevitable conversion to an IPv6 infrastructure to allow for more possible addresses, Cisco introduced the Network Address Translator (RFC 1631). A NAT gateway sits on the border between private and public networks, converting private addresses defined by RFC 1918 into legally registered public IP addresses allocated by IANA. This means that an entire group of hosts can be represented by a single unique IP address to anything outside their network. NAT is commonly supported by WAN access routers and firewalls. |