Cisco Systems, Inc. Cisco Systems, Inc. Aramco This document describes how PIM Sparse-Mode can be used to construct IPv4 multicast trees across an IPv6-only network core. This allows forwarding of native IPv4 multicast data packets. The document specifies how to send and receive IPv4 PIM messages with IPv6 headers, using a new well-known link-local IPv6 multicast address, and the use of RPF vectors for reachability.