Connecting Multicast Islands with GRE

This post covers how to join together devices requiring multicast connectivity across networks that do not support multicast. This situation is common when the Internet is used for transport, and even in private networks such as MPLS L3VPN if the carrier does not support multicast (or you decided not to pay extra for that service). I will be using Cisco devices and GRE tunnels, though the concepts are generic and apply to…