RFC 1631 The IP Network Address Translator (NAT)
Internet Engineering Task Force, (May 1994)Abstract
The two most compelling problems facing the IP Internet are IP
address depletion and scaling in routing. Long-term and short-term
solutions to these problems are being developed. The short-term
solution is CIDR (Classless InterDomain Routing). The long-term
solutions consist of various proposals for new internet protocols
with larger addresses.
It is possible that CIDR will not be adequate to maintain the IP
Internet until the long-term solutions are in place. This memo
proposes another short-term solution, address reuse, that complements
CIDR or even makes it unnecessary. The address reuse solution is to
place Network Address Translators (NAT) at the borders of stub
domains. Each NAT box has a table consisting of pairs of local IP
addresses and globally unique addresses. The IP addresses inside the
stub domain are not globally unique. They are reused in other
domains, thus solving the address depletion problem. The globally
unique IP addresses are assigned according to current CIDR address
allocation schemes. CIDR solves the scaling problem. The main
advantage of NAT is that it can be installed without changes to
routers or hosts. This memo presents a preliminary design for NAT,
and discusses its pros and cons.
