IPv6-to-IPv6 Network Prefix Translation

IPv6-to-IPv6 Network Prefix Translation

Communication protocol
File:Nat66.drawio.png
Purpose	Network address translation
Introduction	2011 (2011)
RFC(s)	6296, 7157...
Website	{{#property:P856}}

IPv6-to-IPv6 Network Prefix Translation (NPTv6) is a specification for IPv6 to achieve address-independence at the network edge, similar to network address translation (NAT) in Internet Protocol version 4 (IPv4). It has fewer architectural problems than IPv4 NAT; for example, it is stateless, uses a 1:1 address mapping and preserves the reachability attributed to the end-to-end principle. However, because the new address is chosen in a way that leaves the checksum unchanged (checksum-neutral mapping) the interface identifier bits change and this may break applications that embed data in them (such as IPsec). Additionally, split-horizon DNS may be required for use in a business environment.

File:NPTv6 Multihoming.png

NPTv6 multihoming example

NAT66

NAT66 was the name used in earlier drafts of the standard. There were some initial proposals to rename it, and a few years later the name NPTv6 was chosen. One of the early versions defined two modes of operation within NAT66: a Two-Way Algorithmic mapping and a Topology Hiding Option, the latter of which used a non-reversible address mapping that would've required additional state in the translator, either in the form of a dynamic table or a statically defined set of address mappings. It was soon removed, leaving the two-way mapping as the only mode of operation and making the specification fully stateless.

Current usage of the term (by vendors, in informal contexts, etc.) is unclear: sometimes it's still employed as a synonym for NPTv6 but often it refers to a generic implementation of stateful NAT (or even full NAPT) on IPv6.

External links

• Cisco documentation on NPTv6
• Juniper documentation on NPTv6
• VyOS documentation on NPTv6
• OPNsense documentation on NPTv6
• APNIC blog post from 2018 on NAT66
• pfSense documentation on NPt