Linux Firewalls, Third Edition

The Conceptual Background of NAT

NAT was first presented in 1994 in RFC 1631, which was later replaced by RFC 3022. NAT was proposed as a possible short-term, temporary solution (to be used until IPv6 was deployed) to the growing shortage of public IP addresses. NAT also was seen as a possible solution to the growing demands on routers that handled noncontiguous address blocks. It was thought that NAT might possibly reduce or eliminate the need for CIDR, which, in turn, was prompting address reallocations and changes to router software and network configurations. NAT was also seen as a means to avoid the cost and overhead of local network renumbering when the address spaces were reallocated, or when a site changed service providers and was assigned ...