CHAPTER 1
The problem
Why dynamic PD can force unnecessary renumbering of otherwise stable networks.
Overview
Stable IPv6 despite dynamic Prefix Delegation
Network Prefix Translation for IPv6 allows an internal addressing plan to remain stable even when an ISP changes the prefix used on the public Internet.
Dynamic external addressing should not require dynamic internal addressing.
0.1Purpose of this site
NPTv6.org documents the operational problem created by changing ISP-provided prefixes, explains the conventional ULA-based solution, and presents an alternative model for networks that prefer Global Unicast Address semantics internally.
CHAPTER 2
ULA model
The standards-aligned NPTv6 deployment and its address-selection considerations.
CHAPTER 3
Non-routed GUA
An alternative internal prefix model using first-class GUA semantics.
CHAPTER 4–5
Operations
Address planning, routing controls, limitations, and project provenance.
0.2The two deployment models
| Characteristic | ULA + NPTv6 | Non-routed GUA + NPTv6 |
|---|---|---|
| Stable internal addressing | Yes | Yes |
| Uses an officially defined local-use prefix type | Yes | No |
| Receives normal GUA source-address semantics | Not by default in every dual-stack case | Yes |
| Requires correct NPTv6 edge mapping | Yes | Yes |
| Potential overlap when independent networks interconnect | Possible | Possible |
0.3The operational resource
Intentionally non-routed internal-use prefix
2602:f925:ad::/48
This is not an example prefix. It is the specific GUA block discussed by this document for actual internal use behind NPTv6 by networks that choose this model.
Its useful property is not public reachability. Its useful property is that the block has been deliberately removed from production use and subjected to routing controls intended to keep it dark across public networks.
Routing controls: The entire prefix, including all subdivisions, is covered by a Route Origin Authorization designating AS0 (RFC 6483 / RFC 7607), published under ARIN's hosted RPKI. Any attempt to originate the prefix from any AS is therefore RPKI-invalid and is dropped by validating networks. The prefix is additionally black-holed at the origin AS as a data-plane backstop. Both controls are public and independently verifiable.