NAT helps multiple users share only a few valid public network addresses when the users attempt to access the Internet. NAT configuration is simple and secure.
As the Internet is developed and network applications grow, IPv4 addresses are running out, which constrains network development. Before IPv6 is widely used to replace IPv4 that has been running on various network devices and bearing a majority of existing applications, some IPv4-to-IPv6 transition techniques can be used to alleviate IPv4 address shortage.
NAT translates IP addresses in IP datagram headers between private and public networks when devices on a private network attempt to access the Internet. NAT translates many private IP addresses to a few public IP addresses, which alleviates IP address exhaustion.