Multicast Boundary

There are many ways to control the size of the multicast domain: In this article, we will talk about TTL and multicast boundary command.

• TTL :  we use " ip multicast ttl-threshold  x "  command. When the router receives the multicast packet, it will compare the TTL to the configured value. If the packet TTL is greater than configured TTL, the router will pass the multicast traffic. If not, it will drop. And that is the boundary of the multicast domain.
• Example:   ip multicast ttl-threshold  240
• It will not forward any multicast packet with TTL less than 240

• Multicast Boundary : we use  "ip multicast boundary <access-list>" command at the interface level of the router stating that this interface is the multicast boundary. The router will not send any multicast traffic (matched the access-list) to the downstream router
• Example :   ip mutlicast boundary 15
• Configured the multicast boundary of the access-list 15