14 IntroductionVLAN-aware MAC-based SwitchingPackets arriving from an unknown source address are sent to the microprocessor, where the source addressesare added to the Hardware Table. Packets addressed to or from this address are more efficiently forwardedusing the Hardware Table.MAC Multicast SupportMulticast service is a limited broadcast service, which allows one-to-many and many-to-many connectionsfor information distribution. Layer 2 Multicast service is where a single frame is addressed to a specificMulticast address, from where copies of the frame are transmitted to the relevant ports. IGMP Snooping issupported, including IGMP Querier which simulates the behavior of a multicast router, allowing snooping ofthe layer 2 multicast domain even though there is no multicast router.For more information, see "Multicast Forwarding Support" on page 328.Layer 2 FeaturesIGMP SnoopingInternet Group Membership Protocol (IGMP) Snooping examines IGMP frame contents, when they areforwarded by the device from work stations to an upstream Multicast router. From the frame, the deviceidentifies work stations configured for Multicast sessions, and which Multicast routers are sending Multicastframes.For more information, see "IGMP Snooping" on page 339.Port MirroringPort mirroring monitors and mirrors network traffic by forwarding copies of incoming and outgoing packetsfrom a monitored port to a monitoring port. Users specify which target port receives copies of all trafficpassing through a specified source port.For more information, see "Defining Port Mirroring Sessions" on page 264.Broadcast Storm ControlStorm Control enables limiting the amount of Multicast and Broadcast frames accepted and forwarded bythe device.When Layer 2 frames are forwarded, Broadcast and Multicast frames are flooded to all ports on the relevantVLAN. This occupies bandwidth, and loads all nodes connected on all ports.For more information, see "Enabling Storm Control" on page 261.
