Dell EMC SmartFabric OS10 User Guide Release 10.5.0

Internet Group Management Protocol

Internet Group Management Protocol (IGMP) is a communications protocol that establishes multicast group memberships using IPv4 networks. OS10 supports IGMPv1, IGMPv2, and IGMPv3 to manage the multicast group memberships on IPv4 networks.

The IGMP querier periodically (by default, every 60 seconds) sends out a membership query to all the hosts. The hosts, in response to the query, send a response back to the querier to report their multicast group memberships. The switch makes an entry to identify the corresponding port as a member of the particular multicast group..

When a host wants to join a multicast group, it sends an IGMP message to the multicast router.

Each network segment has an IGMP querier, which is a multicast router. The multicast router periodically sends IGMP queries to learn which multicast groups are active and have members on the network.

Multicast routers send the following types of queries:

• General query—To learn about listeners for multicast groups.
• Multicast address-specific query—To learn if a particular multicast address has listeners.
• Multicast address-and-source-specific query—To learn if any of the sources from the specified list for a multicast source has any listeners.

The hosts send the following messages to multicast routers:

• Version 1: Membership report
• Version 2:
  • Version 1 membership report for backward compatibility with version 1
  • Version 2 membership report
  • Leave group message
• Version 3:
  • Version 1 membership report for backward compatibility with version 1
  • Version 2 membership report for backward compatibility with version 2
  • Version 3 membership report
  • Version 2 leave group message

  Version 3 provides support for source filtering. The system reports interest in receiving packets only from specific source addresses, or from all the sources except some specific source addresses, sent to a particular multicast address.