Some posts on example domains and example IP-ranges (IPv4 and IPv6)
Posted by jpluimers on 2025/05/05
Here are some of my blog posts on documenting using example domains and example IP-addresses or IP-ranges:
- RFC2606: Reserved Top Level DNS Names (RFC); draft-ellermann-idnabis-test-tlds-04: Reserved Top Level DNS Names (Internet-Draft, 2008)
- A url or site like example.org which always produces a 404 error (and two for 200 and 204)
- Example.[com|net|org] Web Page
- The Bogon Reference – Team Cymru
(I really wish that example.org and others would service SMTP with blackhole routing so one can also use it for bogus email addresses in documentation)
The blog posts above were incomplete (IPv6 was missing; IPv4 was not explained), so below are more links that do a better job based on a Tweet from [Wayback/Archive] Julia Evans (@b0rk).
I put all of these in one place for easier reference.
- IPv4 documentation subnets from Reserved IP addresses: IPv4 – Wikipedia
Special address blocks Address block Address range Number of addresses Scope Description 192.0.2.0/24 192.0.2.0–192.0.2.255 256 Documentation Assigned as TEST-NET-1, documentation and examples. 198.51.100.0/24 198.51.100.0–198.51.100.255 256 Documentation Assigned as TEST-NET-2, documentation and examples. 203.0.113.0/24 203.0.113.0–203.0.113.255 256 Documentation Assigned as TEST-NET-3, documentation and examples. 233.252.0.0/24 233.252.0.0-233.252.0.255 256 Documentation Assigned as MCAST-TEST-NET, documentation and examples. - IPv6 documentation subnet from Reserved IP addresses: IPv6 – Wikipedia
Special address blocks Address block (CIDR) First address Last address Number of addresses Usage Purpose 2001:db8::/32 2001:db8:: 2001:db8:ffff:ffff:ffff:ffff:ffff:ffff 296 Documentation Addresses used in documentation and example source code - [Wayback/Archive] ip – Where can I use the IPv6 documentation prefix – Network Engineering Stack Exchange (thanks [Wayback/Archive] sliebald, [Wayback/Archive] mushr00mer1990 and [Wayback/Archive] jcbermu)
…
if you are looking for an equivalent of private IPv4 adresses you should take a look in RFC4193.
There you can see that
fc00::/7is the suitable subnet for testing purposes.…
The IPv6 documentation prefix
(2001:db8:::/32)must be used ONLY for documentation purposes. It means written examples, diagrams, PPT presentations, Textbook explanations, etc.This range shouldn’t be used in practical networks.
There is a “private IP range” of
fc00::/7which should be used for device testing, demos, courses, etc. as per RFC4193Unicast adresses in this range must be used in local networks without access to public internet.
…
example.org/.net/.comdo not (yet) service SMTP, but I’m not the only one who would want them to:- [Wayback/Archive] “example.org” “smtp” – Google Search
- [Wayback/Archive] domain – Where does email sent to *@example.com go? – Server Fault (thanks [Wayback/Archive] bryan kennedy, [Wayback/Archive] Hot Licks, and [Wayback/Archive] eduardocereto)
…
If there’s no MX record, mail servers will attempt deliver to the A record.example.com’s servers don’t listen on port 25, so the mail server won’t establish a TCP connection and won’t even begin delivery.….
IANA owns the domains so even if there’s no MX as of today, IANA may set up one in the future and start receiving emails for example.* domains.
…
- [Wayback/Archive] domain – Where does email sent to *@example.com go? – Server Fault (thanks [Wayback/Archive] bryan kennedy, [Wayback/Archive] Hot Licks, and [Wayback/Archive] eduardocereto)
- [Wayback/Archive] “example.org” “smtp” – Google Search
- [Wayback/Archive] Stiftung Warentest | Unabhängig. Objektiv. Unbestechlich (
test.de). test consumer products, and is not for internet documentation purposes nor web-testing. - [Wayback/Archive] SIDN:
example.nl
Example domain name
This domain name has been registered by SIDN.
You may use it as an example of a domain name. Prior permission is not required. - a
All via
- [Wayback/Archive] Julia Evans on Twitter: “i really love that
example.comis a real domain and its only purpose is to be used in examples”
- [Wayback/Archive] Larry Seltzer on Twitter: “@b0rk
example.netandexample.org too
rfc-editor.org/rfc/rfc2606.html“ - [Wayback/Archive] Dragonfox called Sophie on Twitter: “@b0rk there is also
example.organdexample.netalso, do you already know about2001:db8::/32?”- [Wayback/Archive] bencord0 on Twitter: “@0x0a_fox @b0rk The documentation prefix 🥰”
- [Wayback/Archive] Jeroen Wiert Pluimers @wiert@mastodon.social on Twitter: “@bencord0 @0x0a_fox @b0rk I didn’t know, so thanks for telling what it is. It made me find
networkengineering.stackexchange.com/questions/44121/where-can-i-use-the-ipv6-documentation-prefixLearned a new thing: great!”
- [Wayback/Archive] Seppo Syrjänen on Twitter: “@b0rk There’s an IPv4 address range to be used (only) in (written) documentation, not in live networks. If I remember correctly.”
- [Wayback/Archive] Philip Kendall on Twitter: “@SepeSy @b0rk 3 ranges in fact –
192.0.2.0/24,198.51.100.0/24and203.0.113.0/24datatracker.ietf.org/doc/rfc5737“ - [Wayback/Archive] Jeroen Wiert Pluimers @wiert@mastodon.social on Twitter: “@jorallan @SepeSy @b0rk The 4th is
233.252.0.0/24(MCAST-TEST-NET), seedatatracker.ietf.org/doc/html/rfc5771#section-9.2“
- [Wayback/Archive] Philip Kendall on Twitter: “@SepeSy @b0rk 3 ranges in fact –
- [Wayback/Archive] Floppy on Twitter: “@b0rk In germany we have a Product testing organization with the domain
test.deThey get DDoS attacks more often because some people just usetest.deas target for testing their botnet. I wonder if this is similar for the example domains” - [Wayback/Archive] Stefan Lasiewski on Twitter: “@b0rk Apparently
<anything>.testand<anything>.exampleare also available.rfc-editor.org/rfc/rfc2606.html“ - [Wayback/Archive] 「𝗠𝗮𝗿𝗰𝗼」🚶🏼🐕 on Twitter: “@kmcphillips @b0rk @codinghorror Happy to share that
example.nlalso exists 🇳🇱🌷”
- [Wayback/Archive] Larry Seltzer on Twitter: “@b0rk
--jeroen
Jeroen Wiert Pluimers said
… reposted this!