IP: multicast routing

modulename: ipmr.ko

configname: CONFIG_IP_MROUTE

Linux Kernel Configuration
└─>Networking support
└─>Networking options
└─>IP: multicast routing
In linux kernel since version 2.6.12  
This is used if you want your machine to act as a router for IP
packets that have several destination addresses. It is needed on the
MBONE, a high bandwidth network on top of the Internet which carries
audio and video broadcasts. In order to do that, you would most
likely run the program mrouted. If you haven't heard about it, you
don't need it.

source code: