Configuring IGMP on a Router
A router by default is not configured to support multicast traffic. There are a few basic configuration tasks that need to be performed on Cisco IOS routers in order to enable multicast on the network.
Step 1. Enable multicast routing on the router in global configuration mode.
Step 2. Configure PIM routing on the associated interface(s) in the interface configuration mode. Take into consideration that multicast traffic may traverse many different paths and it is always a good idea to enable it on every interface that may need to participate. This might save you some troubleshooting time in the future. When you configure an interface for PIM, it is automatically configured to use IGMPv2 on most current operating systems.
ip pim sparse-mode
On Cisco switches, IGMP version 2 is enabled by default.
Step 3. If necessary, change the IGMP version supported on an interface.
ip igmp version [1,2,3]