In order for Udp multicast to work, router must support it?

Question

I am wondering for the udp multicast to work, router must support it?

Answer 1

Multicast is based on dynamically generated trees that can (theoretically) span the entire internet. These multicast trees are based on two protocols:

• IGMP: Internet Group Management Protocol. Used by receivers and users like me and you.
• PIM: Protocol Independent Multicast. Used by routers to replicate and reroute the packets accordingly.

The client needs to be IGMP-compatible, and the routers need to be PIM-compatible.

Answer 2

To be precise, you will need a multicast router if you want the traffic to traverse different subnets. Normally you can expect multicast to work fine on your local subnet.

Side note, many layer 2-3 switches do not include multicast routing functionality, they can however forward to an external multicast router. Multicast routing can be enabled in CISCO routers, etc.