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192.0.0.170/32

192.0.0.170 is a 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

192.0.0.170 is a well-known address used to discover a network’s NAT64 prefix.

Block192.0.0.170/32
First – last192.0.0.170 – 192.0.0.170
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 has devices on IPv6-only networks look up the name ipv4only.arpa, which resolves to 192.0.0.170 and 192.0.0.171. The IPv6 answer a DNS64 server synthesises for it reveals the NAT64 prefix in use.

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