CODEWITHSUNDEEP
routesudpmulticastgateway
fiedel
fiedel

Reputation: 153

How does a gateway forward UDP multicast packets?

I implemented test programs to send/receive UDP packets through multicast using 224.x.x.x IP address. The server and the client are in the same 192.x.x.x/24 subnet and the server receives UDP packets from the client as expected. I'm curious how the gateway forwards such multicast packets. When the client sets socket option to enable multicast, does it notify the gateway that it's joining a specific group? If not, how does the gateway know which computer is the recipient of the multicast packets - does it broadcast these packets to all computers in the subnet?

Upvotes: 0

Views: 335

Answers (1)

fiedel
fiedel

Reputation: 153

From Wireshark: when a UDP client configures the socket for multicast, the system sends a IGMP packet announcing it joining the group. This way the switch knows the multicast group it is in.

Upvotes: 0

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