NAT is a confusing technology. Many people have difficulties understanding it. Myself included. This causes problems during configuration and troubleshooting. This post is for me to put everything in order and help myself understand NAT. Terminology When using NAT you work with several terms: Inside Local Inside Global Outside Local Outside Global Inside Local The inside local address is an address on the inside of your network. Most of the time these are RFC1918 addresses and are not routable on the internet.