Huawei Quidway S3000-EI Series Operation Manual page 97

Operation Manual - Multicast
Quidway S3000-EI Series Ethernet Switches
II. Implement Layer 2 multicast with IGMP Snooping
The Ethernet switch runs IGMP Snooping to listen to the IGMP messages and map the
host and its ports to the corresponding multicast group address. To implement IGMP
Snooping, the Layer 2 Ethernet switch processes different IGMP messages in the way
illustrated in the figure below:
A router
running IGMP
A Ethernet Switch
running IGMP Snooping
Figure 2-3 Implement IGMP Snooping
1) IGMP general query message: Transmitted by the multicast router to the multicast
group members to query which multicast group contains member. When an IGMP
general query message arrives at a router port, the Ethernet switch will reset the
aging timer of the port. When a port other than a router port receives the IGMP
general query message, the Ethernet switch will notify the multicast router that a
port is ready to join a multicast group and starts the aging timer for the port.
2) IGMP specific query message: Transmitted from the multicast router to the
multicast members and used for querying if a specific group contains any member.
When received IGMP specific query message, the switch only transmits the
specific query message to the IP multicast group which is queried.
3) IGMP report message: Transmitted from the host to the multicast router and used
for applying to a multicast group or responding to the IGMP query message. When
received the IGMP report message, the switch checks if the MAC multicast group,
corresponding to the IP multicast group the packet is ready to join exists. If the
corresponding MAC multicast group does not exist, the switch only notifies the
router that a member is ready to join a multicast group, creates a new MAC
multicast group, adds the port received the message to the group, starts the port
aging timer, and then adds all the router ports in the native VLAN of the port into
the MAC multicast forwarding table, and meanwhile creates an IP multicast group
and adds the port received the report message to it. If the corresponding MAC
Internet
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2-3
Chapter 2 IGMP Snooping Configuration
IGMP packets
IGMP packets