IPv6 Address Prefixes Reserved for Documentation

[RFC3849] specified an IPv6 prefix to be used in documentation, in order to reduce the likelihood of conflict and confusion when relating examples of deployed systems. This prefix was reserved to be used in examples in RFCs, books, documentation, and the like. It became widely accepted and used. Although the IPv6 documentation prefix proved to be very useful, a / 32 prefix is not enough to be used to document some kinds of IPv6 deployments, such as large ISP deployments, transition techniques, and other useful examples that require longer prefixes. This document defines the allocation of a new global unicast (GUA) block and a new unique local (ULA) block, to expand the range of documentation blocks. It also updates [RFC3849].