Last Updated: Wednesday, 8 June 2022 By: Steve Warner

As mentioned previously, the term inside refers to those networks that are owned by an organization and that must be translated. Inside this domain, hosts will have address in the one address space, while on the outside, they will appear to have addresses in a another address space when NAT is configured. The first address space is referred to as the local address space while the second is referred to as the global address space.

Similarly, outside refers to those networks to which the stub network connects, and which are generally not under the organization's control. As will be described later, hosts in outside networks can be subject to translation also, and can, thus , have local and global addresses.

To summarize, NAT uses the following definitions:

inside local address--The IP address that is assigned to a host on the inside network. The address is probably 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 repre sents 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 n ecessarily a legitimate address, it was 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's owne r. The address was allocated from globally routable address or network space.