Network Address Translation (NAT)

NAT provides a method of assigning and distributing internal and external addresses and traffic, in the sense that several computers in a workgroup can use the same public address when they are given private addresses by the NAT router.

NAT converts an internal address to a public address.

When set up, NAT has the following characteristics:

• Uses one interface (port) for incoming and outgoing external traffic.

• Uses one interface (port) for incoming and outgoing internal traffic.

• Can be a physical interface (for example, Ethernet-to-Internet and AirPort-to-internal traffic).

• Can be a virtual interface (for example, an Ethernet card can be assigned two IP addressesone external and one internal).

Devices providing NAT (sometimes called gateways) include cable/DSL (Digital Subscriber Line) modems and routers.

NAT can be enabled by selecting the "Share your Internet connection" checkbox in the Internet pane of Sharing preferences. This makes your computer act as a go-between for all information to and from the Internet using your Internet connection.