Reserved IP Addresses and Domain Names

by Scott Wilson on September 22, 2014

When I first started writing about networking, I set up the software on the company network and took screen grabs of that setup.

It quickly became apparent that putting real IP addresses and URLs into our user documentation was, in technical terms, a “bad idea.”

So my Tech Pubs team instituted a policy of changing the IP addresses and URLs that went in the documentation using Photoshop. I’m not sure whose IP addresses and URLs we ended up using, but we knew they weren’t ours, so we were OK with it.

Turns out, we didn’t need to do that. The people who run the Internet knew of our issue and had solved it in advance.

Specifically, there are three sets of IP addresses that are reserved for, among other uses, documentation usage:

  • 192.0.2.0 – 192.0.2.255, called TEST-NET and defined in RFC 5737 (tools.ietf.org/html/rfc5737).
  • 198.51.100.0 – 198.51.100.255, called TEST-NET-2, also defined in RFC 5737
  • 203.0.113.0 – 203.0.113.255, called TEST-NET-3, also defined in RFC 5737

They don’t route, so if your readers use them, but they won’t actually do anything.

For more information, refer to the Wikipedia entry Reserved IP addresses (en.wikipedia.org/wiki/Reserved_IP_addresses).

In addition, there are domain names reserved for documentation use per RFC 2606:

  • example.com
  • example.net
  • example.org
  • example.edu

They can be used for URLs and email addresses.

For more information, refer to the Wikipedia entry example.com (en.wikipedia.org/wiki/Example.com).

Bottom line, use these reserved IP addresses and domain names and not Photoshop for your networking screen grabs.

{ 0 comments… add one now }

Leave a Comment

Previous post:

Next post: