82 Switch FeaturesInternet Small Computer System Interface (iSCSI) OptimizationThe iSCSI Optimization feature helps network administrators track iSCSItraffic between iSCSI initiator and target systems. This is accomplished bymonitoring, or snooping traffic to detect packets used by iSCSI stations inestablishing iSCSI sessions and connections. Data from these exchanges mayoptionally be used to create classification rules to assign the traffic betweenthe stations to a configured traffic class. This affects how the packets in theflow are queued and scheduled for egress on the destination port.For information about configuring iSCSI settings, see "Configuring iSCSIOptimization" on page 395.Layer 2 Multicast FeaturesFor information about configuring L2 multicast features, see "Configuring L2Multicast Features" on page 695.MAC Multicast SupportMulticast service is a limited broadcast service that allows one-to-many andmany-to-many connections. In Layer 2 multicast services, a single frameaddressed to a specific multicast address is received, and copies of the frameto be transmitted on each relevant port are created.IGMP SnoopingInternet Group Management Protocol (IGMP) Snooping is a feature thatallows a switch to forward multicast traffic intelligently on the switch.Multicast traffic is traffic that is destined to a host group. Host groups areidentified by the destination MAC address, i.e. the range 01:00:5e:00:00:00 to01:00:5e:7f:ff:ff:ff for IPv4 multicast traffic or 33:33:xx:xx:xx:xx for IPv6multicast traffic. Based on the IGMP query and report messages, the switchforwards traffic only to the ports that request the multicast traffic. Thisprevents the switch from broadcasting the traffic to all ports and possiblyaffecting network performance.
