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Chapter 15 IGMP Snooping
15.1 Introduction to IGMP Snooping
IGMP (Internet Group Management Protocol) is a protocol used in IP multicast.
IGMP is used by multicast enabled network device (such as a router) for host
membership query, and by hosts that are joining a multicast group to inform the router to
accept packets of a certain multicast address. All those operations are done through
IGMP message exchange. The router will use a multicast address (224.0.0.1) that can
address to all hosts to send a IGMP host membership query message. If a host wants to
join a multicast group, it will reply to the multicast address of that a multicast group with a
IGMP host membership reports a message.
IGMP Snooping is also referred to as IGMP listening. The switch prevents multicast
traffic from flooding through IGMP Snooping, multicast traffic is forwarded to ports
associated to multicast devices only. The switch listens to the IGMP messages between
the multicast router and hosts, and maintains multicast group forwarding table based on
the listening result, and can then decide to forward multicast packets according to the
forwarding table.
ES4700 series provides IGMP Snooping and is able to send a query from the switch
so that the user can use ES4700 series in IP multicast.
15.2 IGMP Snooping Configuration Task
1. Enable IGMP Snooping
2. Configure IGMP Snooping
3. Configure sending of IGMP Query
1. Enable IGMP Snooping
Command Explanation
Global Mode
ip igmp snooping
no ip igmp snooping
Enables IGMP Snooping
2. Configure IGMP Snooping
Command Explanation
