3fff:0:0:0:0:0:0:0/20

This block is reserved for documentation and examples. It gives writers safe IPv6 space to use in tutorials, diagrams, tickets, and sample configuration without pointing readers at a real organization.

This block is not expected to be globally reachable. It should not be assigned to real hosts, advertised in BGP (Border Gateway Protocol), or appear as working Internet traffic.

A system administrator is likely to encounter 3fff::10 or another RFC 9637 documentation space address while reading documentation, reviewing training material, or sanitizing logs. In production data, it usually means placeholder text was copied into a live system.

Firewall tip: documentation ranges are normally treated as invalid in real traffic and dropped at Internet edges.