24 Introduction
IGMP Snooping
Internet Group Management Protocol (IGMP) Snooping is a feature that allows a switch to forward
multicast traffic intelligently on the switch. Multicast I P traffic is traffic that is destined to a host group.
Host groups are identified by class D IP addresses, which range from 224.0.0.0 to 239.255.255.255. Based
on the IGMP query and report messages, the switch forwards traffic only to the ports that request the
multicast traffic. This prevents the switch from broadcasting the traffic to all ports and pos sibly affecting
network performance.
Port Mirroring
Port mirroring monitors and mirrors network traffic by forwarding copies of incoming and outgoing
packets from up to four source ports to a monitoring port.
Broadcast Storm Control
When Layer 2 frames are forwarded, broadcast, unknown unicast, and multicast frames are flooded to all
ports on the relevant virtual local area network (VLAN). The flooding occupies bandwidth, and loads all
nodes connected on all ports. Storm control limits the amount of broadcast, unknown unicast, and
multicast frames accepted and forwarded by the switch.