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 typically would be your router interface connected to your ISP. The latter is usually a public address and is how the packet begins its journey.
After translation, the inside local address is then called the inside global address and the outside ...