Connectivity Guide

Usage Information
Multicast snooping ood control, IGMP snooping, and MLD snooping are enabled by default.
For multicast ood restrict to be eective on a VLAN, IGMP snooping and MLD snooping must be enabled at both
global and VLAN levels.
To disable multicast snooping ood control, use the no multicast snooping flood-restrict command.
Example
OS10(config)# multicast snooping flood-restrict
Supported Releases 10.4.3.0 or later
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..
NOTE: A multicast router is a Layer 3 router or switch that has multicast features enabled.
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-specic query—To learn if a particular multicast address has listeners.
• Multicast address-and-source-specic query—To learn if any of the sources from the specied 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 ltering. The system reports interest in receiving packets only from specic source addresses, or
from all the sources except some specic source addresses, sent to a particular multicast address.
Standards compliance
• OS10 complies to the RFCs 1112, 2236, and 3376 for IGMP versions 1, 2, and 3, respectively.
620
Multicast