User's Manual

Configuration Guide of XGS-5240-Series
42-13
 Afterwards, to assure to start a kind of multicast protocol on the interface;
 Multicast Protocol requires RPF Check using unicast routing; therefore the correctne
ss of unicast routing must be assured beforehand.
42.3 IGMP Snooping
42.3.1
Introduction to IGMP Snooping
IGMP (Internet Group Management Protocol) is a protocol used in IP multicast. IG
MP is used by multicast enabled network device (such as a router) for host membershi
p 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 me
ssage exchange. The router will use a multicast address (224.0.0.1) that can address t
o all hosts to send an 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
n 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 ass
ociated to multicast devices only. The switch listens to the IGMP messages between th
e multicast router and hosts, and maintains multicast group forwarding table based on t
he listening result, and can then decide to forward multicast packets according to the f
orwarding table.
Switch provides IGMP Snooping and is able to send a query from the switch so th
at the user can use switch in IP multicast.
42.3.2 IGMP Snooping Configuration Task List
1. Enable IGMP Snooping
2. Configure IGMP Snooping
1. Enable IGMP Snooping
Command
Explanation
Global Mode
ip igmp snooping
no ip igmp snooping
Enables IGMP Snooping. The no operation
disables IGMP Snooping function.
2. Configure IGMP Snooping