IP addresses in documentation

Everybody knows about RFC 1918.

It sets aside three IPv4 network ranges for "private use".

That means you can use these ranges on your own networks, for internal (non-public) use, and do whatever you like with them (subnet them, allocate them to hostnames in DNS, route them over VPNs, whatever), however you cannot route them over the public Internet (except via some sort of tunnel which hides these addresses from the Internet's routers).

The ranges are:

• 10.0.0.0/8
• 172.16.0.0/12
• 192.168.0.0/16

However, RFC 5737 specifies a few other address ranges available for "documentation purposes".

This means you shouldn't really use them on real networks (even private ones), although they'll certainly work if you do, but you should use these network ranges for documentation (eg: writing books or HOWTOs, posting on mailing lists and obscuring your own addresses if you feel the need to, and generally giving examples of "an IPv4 address goes here" without specifying an address which could well be in use by someone, somewhere).

These ranges are:

• 192.0.2.0/24
• 198.51.100.0/24
• 203.0.113.0/24

Please do use them whenever you're giving examples and don't (perhaps inadvertently) want to show a valid IP public address.

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