Sign inMonitor a domain
100::/64

100

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

Short answer

100::/64 is the IPv6 discard prefix: traffic sent there is meant to be dropped.

Block100::/64
First – last100:: – 100::ffff:ffff:ffff:ffff
Sizea /64 (2^64 addresses)
Name in the registryDiscard-Only Address Block
Defined inRFC 6666
Allocated2012-06
Valid as source / destinationTrue / True
ForwardableTrue
Globally reachableFalse

What it means

RFC 6666 reserves it so network operators can blackhole unwanted traffic with a standard prefix.

Nothing legitimate lives there.

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

Sources

  1. IANA IPv6 Special-Purpose Address Registry (CC0) · checked 2 Nov 2026
  2. RFC 6666