What is IGMP Snooping and how does it improve network efficiency?

Zyxel_Nami Posts: 479  Zyxel Employee
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IGMP Snooping is a network switch feature that listens to Internet Group Management Protocol (IGMP) traffic to optimize the distribution of multicast streams. Without IGMP Snooping, multicast streams are indiscriminately sent to all ports, which can cause network congestion and waste bandwidth.

For instance:

  • Without IGMP Snooping, as shown on the left side of the above illustration: if Host A joins Channel 1(, the media server sends the stream to all connected hosts, regardless of whether they have requested the stream or not. As a result, Host B, which did not request any content, also receives the Channel 1 stream, leading to excessive traffic on the network.
  • With IGMP Snooping enabled, as shown on the right side of the illustration: if Host A reports to join Channel 1, the switch, which supports IGMP Snooping, will consult its multicast table and forward the stream exclusively to Host A. Host B, which has not requested to join the multicast group for Channel 1, will not receive any of the streams, thus conserving bandwidth and preventing unnecessary network traffic.

Zyxel Nami