Routing IP Multicast Traffic Overview

By Edward Tetz from Cisco Networking All-in-One For Dummies

IP Multicast Routing is a huge topic because several technologies are at use in IP Multicast Routing, which means that space permits me to give only a cursory explanation of how this technology works. All networks function fine without multicast routing, but you may find some benefit to enabling it on your network.

IP Multicast Data is data that is sent out to a large group of computers but travels over the network as a single network frame. It is typically managed at the data link layer as a broadcast, though it needs to reach only a subset of all computers on the network. IP Multicast Routing is the routing of the multicast traffic.

Some situations that will benefit from enabling multicast routing include networks or companies that want to make use of the following:

Multicast imaging solutions for desktop OS deployment implemented across routers. These solutions often work if the solution is limited to a single network segment.
Music on Hold and some other features of IP-based phone systems. Although you may be able to implement this as a unicast solution, multicast will greatly reduce network utilization.
Multimedia steaming solutions that allow for multicast transmission.
With routing protocols that send data to systems in an area or AS via multicast. Typically, these messages only need to go as far as the local data link, so no routing will be required.