Documentation IP and Domain Generator

Why an arbitrary IP address is the wrong example

When a runbook or a slide needs an example IP address, a number made up on the spot is an address that someone in the world is actually using. A reader copies it, runs a connectivity check or applies a configuration, and the traffic goes to an unrelated third party. The same happens with domain names. If someone has registered the placeholder domain written in an internal document, mail sent to it arrives at their server.

To avoid this, the IETF reserves values for use in documentation. Reserved ranges are not routed and are never assigned to anyone. Pasting them into a runbook, or even running the commands, reaches nothing. This tool draws only from those reserved ranges.

Reserved ranges

Choosing between them

The three IPv4 blocks carry no difference in meaning; there are simply three of them. When one diagram has several actors, such as your side, the far side and a device on the path, giving each actor its own block keeps the reader from mixing them up. IPv6 has only 2001:db8::/32, so split it into /48 or /64 pieces instead.

Private addresses such as 10.0.0.0/8 are not documentation ranges. The reader is likely using them already, so a pasted example can point at another machine inside their own network. Use the reserved ranges for examples, and write private addresses in a way that makes clear the reader must substitute their own value.