This document specifies an extension to the multicast addressing architecture of the IPv6 protocol. The extension allows the use of Interface Identifiers (IIDs) to allocate multicast addresses. When a link-local unicast address is configured at each interface of a node, an IID is uniquely determined. After that, each node can generate its unique multicast addresses automatically without conflicts. The alternative method for creating link-local multicast addresses proposed in this document is better than known methods like unicast-prefix-based IPv6 multicast addresses. This memo updates RFC 3306. [STANDARDS-TRACK]