In this article, we are going to look at a topic that, in my experience, is not well known. There are IP and MAC ranges that are reserved for documentation and can’t be routed. There are many use cases for these ranges.

Use Cases

There are several reasons why you don’t want to use real or accessible host addresses. Perhaps the biggest reasons are for Security & Privacy: you want to avoid sharing sensitive information or running scripts against ‘real’ host addresses.

More examples:: Documentation - in scripts, manuals, articles, …; Placeholder - in firewall policies, scripts, templates, …; Mock-up - in product demonstrations, presentations, flyers, …; Sanitize / Anonymize Data - logs, packet captures, configuration files, …

There are more, but you know where I am going with this.

Important: Just to mention it again, please do not use the following address for anything else to avoid problems.

IP Addresses

IPv4 has the following IP address ranges:

TEST-NET-1 - 192.0.2.0/24 (192.0.2.0–192.0.2.255)

TEST-NET-2 - 198.51.100.0/24 (198.51.100.0–198.51.100.255)

TEST-NET-3 - 203.0.113.0/24 (203.0.113.0–203.0.113.255)

Referenced in the RFC5737.

For Any-Source Multicast (ASM):

MCAST-TEST-NET - 233.252.0.0/24 (233.252.0.0–233.252.0.255)

Noted, that it is part of the normal multicast space and referenced in RFC6676.

You have two ranges in IPv6:

2001:db8::/32
- Start: 2001:db8::
- End: 2001:db8:ffff:ffff:ffff:ffff:ffff:ffff
- Referenced in RFC3849
3fff::/20
- Start: 3fff::
- End: 3fff:fff:ffff:ffff:ffff:ffff:ffff:ffff
- Referenced in RFC9637