NAT:

• NAT stands for Network Address Translation. NAT is a way to map an entire networks to a single IP address.
• NAT is necessary when the number of IP addresses assigned to you by your Internet Service Provider is less than the total number of computers that you wish to provide internet access for.
• Network Address Translation is designed for IP address conservation. It enables private IP networks that use unregistered IP addresses to connect to the Internet.
• NAT operates on a router, usually connecting two networks together, and translates the private (not globally unique) addresses in the internal network into legal addresses, before packets are forwarded to another network.
• As part of this capability, NAT can be configured to advertise only one address for the entire network to the outside world. This provides additional security by effectively hiding the entire internal network behind that address.
• NAT offers the dual functions of security and address conservation and is typically implemented in remote-access environments.
• NAT allows a single device, such as a router, to act as an agent between the Internet (or public network) and a local network (or private network), which means that only a single unique IP address is required to represent an entire group of computers to anything outside their network.
• In order to configure traditional NAT, you need to make at least one interface on a router (NAT outside) and another interface on the router (NAT inside) and a set of rules for translating the IP addresses in the packet headers and payloads if desired need to be configured.
• In order to configure Nat Virtual Interface (NVI), you need at least one interface configured with NAT enable along with the same set of rules.