NAT confers the following advantages:

• NAT conserves public Internet address space.

  Any number of hosts within a local network can use private IP addresses instead of consuming public IP addresses. The addresses of packets that are transmitted from this network to the public Internet are translated to the appropriate public IP address. This translation means that the same private IP address space can be reused within any number of private networks, as shown in the following figure.

• NAT enhances security.

  IP addresses within a private (internal) network are hidden from the public (external) network. This hiding of addresses makes it more difficult for hackers to initiate an attack on an internal host. However, private network hosts are still vulnerable to attack; therefore, NAT is typically combined with firewall functionality.

• NAT is seamless.

  Standard client/server network services work without modification through a NAT-enabled device.

• NAT facilitates network migration from one address space to another.

  The address space within a private network that is having NAT performed on it is independent of the public IP address. This independence means that the private network can be moved to a new public IP address without changing network configurations within the private network. Likewise, the addressing within the private network can change without affecting the public IP address.

• NAT simplifies routing.

  NAT reduces the need to implement more complicated routing schemes within larger local networks.