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2001::/32

2001

Last updated 2 Nov 2026 from the IANA IPv6 Special-Purpose Address Registry

Short answer

2001::/32 is Teredo, an old tunnelling mechanism that carried IPv6 over IPv4.

Block2001::/32
First – last2001:: – 2001:0:ffff:ffff:ffff:ffff:ffff:ffff
Sizea /32 (2^96 addresses)
Name in the registryTEREDO
Defined inRFC 4380; RFC 8190
Allocated2006-01
Valid as source / destinationTrue / True
ForwardableTrue
Globally reachableN/A

What it means

RFC 4380 defined Teredo so a computer behind NAT could reach IPv6. Windows used it for years before native IPv6 became common.

A Teredo address embeds the client’s public IPv4 and port in obfuscated form.

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Sources

  1. IANA IPv6 Special-Purpose Address Registry (CC0) · checked 2 Nov 2026
  2. RFC 4380; RFC 8190