Network address translation (NAT) is an IP address translation technology that allows multiple private network users to share a few public IPv4 addresses to access public networks. A NAT device translates private IPv4 addresses in packets to public IPv4 addresses and records the mapping before users access the Internet.
To meet high requirements for NAT specifications on carrier networks, carrier-grade NAT (CGN) is used. CGN is deployed on core routers or broadband remote access servers (BRASs) on carrier networks.
As the Internet is being developed and the network applications are growing, IPv4 address exhaustion constrains network development. Before IPv6 can be widely used to replace IPv4 that has been running on network devices and is bearing existing applications, some IPv4-to-IPv6 transition techniques can be used to alleviate IPv4 address shortage.
NAT provides a transition solution of repeatedly using IPv4 addresses that slows down the tendency towards IPv4 address exhaustion, which helps IPv4 users and services to be transitioned to IPv6.
NAT is mature and easy to deploy.
Existing customer premises equipment (CPE) devices do not need to be upgraded, saving the cost.