Public or Reserved? #296

One address per round. Is it routable on the public internet, or did an RFC set it aside for something else — a private network, a loopback, a documentation range, the space behind a carrier's NAT?

Every answer here is a fact, not a guess. The reserved addresses come from the IANA IPv4 Special-Purpose Address Registry and its IPv6 counterpart, and the RFC that reserved each block is named when you answer. The public addresses are the ones their operators publish themselves. Nothing is looked up while this page loads.

Is this address on the public internet?

149.112.112.112

Pick the one you think is right.

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What the answer was

Block
149.112.112.112
Reserved for
Public — Quad9
Defined by
Globally reachable
Yes
Size
one address
Why that is the answer

149.112.112.112 is a public address — it is really on the public internet.

149.112.112.112 is Quad9 (https://quad9.net/) — one of the addresses its operator publishes for everyone to use. It is on the public internet, and that is exactly why it is such a good thing to know: it is a fixed point in the DNS.


What the round is about

Most of the address space is not public. The IANA registry is the table that says so, and it is the first thing a network engineer checks before telling a colleague "yes, 10.0.0.1 is fine for that". The blocks worth knowing by heart are short:

  • 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 — the three private-use blocks of RFC 1918. They never touch the public internet.
  • 100.64.0.0/10 — carrier-grade NAT space (RFC 6598). Not private in the RFC 1918 sense, but not public either: it is shared between an ISP and its customers. A home router showing one is behind CGNAT.
  • 127.0.0.0/8 — loopback. A packet sent there is handled by your own machine and never leaves it.
  • 169.254.0.0/16 — link-local. A host invented this address itself after no DHCP server answered, so it on a screen is the classic symptom of a broken DHCP handshake.
  • 192.0.2.0/24, 198.51.100.0/24 and 203.0.113.0/24 — TEST-NET-1, -2 and -3, reserved for documentation, so they can never belong to anybody. They are the addresses you will see in every example on the internet.
  • 240.0.0.0/4 — reserved for future use, and never used.

The IPv6 ones are the same idea: fe80::/10 is link-local (the 169.254 equivalent), fc00::/7 is the IPv6 private-use block, and ::1 is loopback.

A block being reserved says what the address space is for. It does not say who is using an address inside it today, and it says nothing at all about where a person is — which is what this page is about when the answer is wrong.

This is the daily round, the same for everyone on 2026-10-23. /reserved.htm?p=1, ?p=2, ?p=3 … walk through the corpus one address at a time.

Like this one? Subnet Sweeper is the same registry reasoning with a mask in it, IPv4 Land Grab shows who was handed the internet, and the network tools will look up a live address for you.

Corpus: IANA IPv4 and IPv6 Special-Purpose Address Registry, frozen 2026-10-21. The reserved blocks and the RFCs are the registry's own; the public addresses are the operators' published ones.


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