IGMP snooping is a switch’s practice of reading the IGMP membership reports that cross it and forwarding each group’s traffic only to the ports on which a member has reported, instead of flooding every multicast frame to every port.
Ejemplos
Example 1.8 (Two groups, one Ethernet address)
Group 239.255.1.2 maps to 01:00:5e:7f:01:02: the low 23 bits of 255.1.2 are 127.1.2 once the top bit of 255 is dropped. Group 224.127.1.2 maps to the same address. A server that joined only the first receives, from any switch or card that filters by Ethernet address alone, the traffic of the second as well. Venues allocate their groups with this in mind, and a firm that runs its own internal multicast (chapter 27’s ticker plant) should too.