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192.0.0.171/32

192.0.0.171 is the second well-known address used to discover a network’s NAT64 prefix.

Last updated 2 Nov 2026 from the IANA IPv4 Special-Purpose Address Registry

Short answer

192.0.0.171 is the second well-known address used to discover a network’s NAT64 prefix.

Block192.0.0.171/32
First – last192.0.0.171 – 192.0.0.171
Size1 addresses
Name in the registryNAT64/DNS64 Discovery
Defined inRFC 8880; RFC 7050, Section 2.2
Allocated2013-02
Valid as source / destinationFalse / False
ForwardableFalse
Globally reachableFalse

What it means

RFC 7050 pairs it with 192.0.0.170 as the two addresses of ipv4only.arpa. Devices use the synthesised IPv6 answers to learn how their IPv6-only network reaches IPv4.

It is never a real host.

Want the address websites actually see for you? Open the Truth Check.

Sources

  1. IANA IPv4 Special-Purpose Address Registry (CC0) · checked 2 Nov 2026
  2. RFC 8880; RFC 7050