What is the 2001:db8::/32 prefix reserved for, and why does it show up everywhere in tutorials?

2001:db8::/32 is the official documentation/example prefix (RFC 3849) — it's guaranteed never to be routed on the real internet, so it's safe to use in books, labs, and configs.

It's the IPv6 analogue of IPv4's documentation ranges (192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24):

• Reserved by RFC 3849 purely for documentation and examples
• Routers and registries treat it as non-routable, so no real traffic can ever reach addresses you write in a tutorial
• That's why lab addresses like 2001:db8:acad:a::1 appear constantly — acad is a common nod to networking academy material

Using it prevents the classic mistake of printing a real customer's prefix in a manual and accidentally encouraging someone to configure it.

Tip: If you see 2001:db8: in any example, it's a "this is just for show" address — never something live.

Go deeper:

• RFC 3849 — IPv6 Address Prefix Reserved for Documentation — defines 2001:db8::/32 as the non-routable documentation prefix.