NAT Names
The names we use to describe the addresses used with NAT are pretty simple. Addresses used
after NAT translations are called
global
addresses. These are usually the public addresses
used on the Internet, but remember, you don’t need public addresses if you aren’t going on the
Internet.
Local
addresses are the ones we use before NAT translation. So, the inside local address is
actually the private address of the sending host that’s trying to get to the Internet, while the
outside local address is the address of the destination host. The latter is usually a public
address (web address, mail server, and so on) and is how the packet begins its journey.
After translation, the inside local address is then called the
inside global address
, and the
outside global address becomes the name of the destination host. Check out Table 8.2, which
lists all this terminology, for a clear picture of the various names used with NAT.
TABLE 8 . 2
NAT Terms
Names Meaning
Inside local Name of inside source address before translation
Outside local Name of destination host before translation
Inside global Name of inside host after translation
Outside global Name of outside destination host after translation