问题
I am wondering for the udp multicast to work, router must support it?
回答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.
回答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.
来源：https://stackoverflow.com/questions/1801621/in-order-for-udp-multicast-to-work-router-must-support-it