PLANET XGS3-24042 - Manual (Page 447)

48-46
 Firstly to assure that physical connection is correct;
 Next, to assure the Protocol of Interface and Link protocol is UP (use show interface command);
 Afterwards, to assure to start a kind of multicast protocol on the interface;
 Multicast Protocol requires RPF Check using unicast routing; therefore the correctness of unicast
routing must be assured beforehand.
48.10 IGMP Snooping
48.10.1 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 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 an 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.
Switch provides IGMP Snooping and is able to send a query from the switch so that the user can use switch in
IP multicast.
48.10.2 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
Command Explanation
Global Mode