NPTv6 using an intentionally non-routed GUA
This alternative model preserves normal Global Unicast Address semantics internally while still insulating the LAN from changes to the ISP-provided prefix.
3.1Architecture
The internal addresses are syntactically and semantically GUA. They are not expected to be reachable directly through public routing; NPTv6 maps them to the ISP-side prefix used for actual Internet communication.
3.2The prefix
The entire /48 may be structured as required by an internal addressing plan. No registration process exists and no exclusive subdivision is granted.
This is an operational resource, not sample notation
The prefix is identified here for actual internal use behind NPTv6 by networks that accept the model and its limitations.
3.3Why not select a random GUA?
An arbitrary GUA may correspond to a legitimate network that is routed today or becomes routed later. Using it internally can make that legitimate destination unreachable from the local network because the internal route wins.
The prefix documented here differs in one essential respect: it has been deliberately excluded from production use under the current operator's control, publicly identified for this purpose, and subjected to routing controls intended to prevent normal global propagation.
3.4What this model provides
| Property | Result |
|---|---|
| Stable internal hierarchy | The /48 remains constant regardless of ISP renumbering. |
| Normal GUA classification | Hosts evaluate the addresses as Global Unicast rather than ULA. |
| Large subnetting space | 256 /56 site blocks or 65,536 /64 LANs are available inside the shared /48. |
| No uniqueness guarantee between users | Independent users may select the same internal subdivision, just as with other shared private-use conventions. |
3.5What this model is not
- It is not an IETF standard or an IANA special-purpose prefix.
- It is not globally unique to any adopting network.
- It is not intended to be announced, routed natively, or used without an appropriate edge translation.
- It is not a guarantee that every routing system worldwide will reject every possible leak.