The brand New IPv6 Documentation Addresses are here!
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by Craig Miller
Since 2004, there has a been a Documentation Prefix for IPv6 (RFC 3849) or 2001:db8::/32. And all though this seems like enough space to allocate for Local Area Networks (LANs), even larger ones, it wasn't good for creating documentation for Autonomous System (AS) to AS connections using Border Gateway Protocol (BGP4). Each AS would have a 2001:db8::/32 address, and that just isn't how routers route.
After twenty (20) years, we finally have a second IPv6 Documentation prefix (RFC 9637: Expanding the IPv6 Documentation Space) or 3fff::/20. The new prefix is still part of the original IPv6 unicast address allocation of 2000::3 (which also includes 3000::/3).
What Are Documentation Prefixes
Not surprisingly, Documentation Prefixes should be used in Documentations. In network examples, both in print and online should be using either RFC 3849 or RFC 9637 address space, or both. Here's an example:
IPv4 Documentation Addresses
Most people use (RFC 1918 Address Allocation for Private Internets) for documenting IPv4 examples. But did you know there are IPv4 addresses specifically allocated for documentation. Back in 2010, RFC 5737 was penned. The following address blocks should be used for IPv4 examples.
- 192.0.2.0/24 (TEST-NET-1)
- 198.51.100.0/24 (TEST-NET-2)
- 203.0.113.0/24 (TEST-NET-3)
Plenty of room to Document
The Internet Assigned Numbers Authority (IANA) has set aside Prefixes for the purpose of of creating examples in documentation. You can find all the IPv6 allocations at IANA's website. The IPv6 documentation prefixes are:
So go forth, and document your network examples, there are 4000 times more Documentation Prefixes available.
Notes:
27 September 2024