5.3 IGMP Snooping
Internet Group Management Protocol Snooping (IGMP Snooping) is a multicast constraining mechanism that runs on
Layer 2 devices to manage and control multicast groups.
The switch, running IGMP Snooping, listens to the IGMP messages transmitted between the host and the router, and tracks
the IGMP messages and the registered port. When receiving IGMP report message, the switch adds the port to the
multicast address table; when the switch listens to IGMP leave message from the host, the router sends the Group-Specific
Query message of the port to check if other hosts need this multicast, if yes, the router will receive IGMP report message;
if no, the router will receive no response from the hosts and the switch will remove the port from the multicast address
table. The router regularly sends IGMP query messages. After receiving the IGMP query messages, the switch will remove
the port from the multicast address table if the switch receives no IGMP report message from the host within a period of
time.
Figure 5-3-1
Unknown multicast data refers to multicast data for which no entries exist in the IGMP Snooping forwarding table. When
the switch receives such multicast traffic:
l With the function of dropping unknown multicast data, the switch drops all the unknown multicast data received.
l With the function of forwarding unknown multicast data, the switch floods unknown multicast data in the VLAN
which the unknown multicast data belongs to.
5.4 Link Aggregation
Link Aggregation is to combine a number of ports together to make a single high-bandwidth data path, so as to implement
the traffic load sharing among the member ports in the group and to enhance the connection reliability.
Figure 5-4-1
To Next Page
Loading...
