NAT address naming conventions

NAT uses various terms to indicate the addresses that are used in NAT. The following definitions clarify their uses:

• Inside local address—The IP address assigned to a host on the inside network. This is the address configured as a parameter of the computer OS or received via dynamic address allocation protocols such as DHCP. The address is likely not a legitimate IP address assigned by the Network Information Center (NIC) or service provider.
• Inside global address—A legitimate IP address assigned by the NIC or service provider that represents one or more inside local IP addresses to the outside world.
• Outside local address—The IP address of an outside host as it appears to the inside network. Not necessarily a legitimate address, it is allocated from an address space routable on the inside.
• Outside global address—The IP address assigned to a host on the outside network by the host owner. The address is allocated from a globally routable address or network space.