Users Guide

290 Network Administration: Multicast
FILE LOCATION: C:\Users\gina\Desktop\Checkout_new\Dell Astute\User
Guide\Dell_Astute_Network_Admin_Multicast.fm
DELL CONFIDENTIAL – PRELIMINARY 8/9/16 - FOR PROOF ONLY
• Unregistered Multicast Group — If traffic addressed to an
unregistered Multicast group is received, it is handled by a special
entry in the Multicast Filtering Database. The default setting of this is
to flood all such traffic (traffic in unregistered Multicast groups).
NOTE: The system supports Multicast filtering for 256 Multicast groups.
Layer 2 Switching
Layer 2 switching forwards Multicast packets received from a VLAN to all the
member ports of the VLAN excluding the source port. While Multicast traffic
forwarding is effective, it is not optimal, as irrelevant ports also receive the
Multicast packets. The excess packets cause increased network traffic.
Multicast forwarding filters enable forwarding of Layer 2 packets to a subset
of ports instead of to all ports.
IGMP Snooping
When IGMP Snooping is enabled globally, all IGMP reports and queries are
forwarded to the CPU. The CPU analyzes the incoming packets and
determines:
• Which ports has hosts that want to join which Multicast groups.
• Which ports have Multicast routers generating IGMP queries.
• What routing protocols are forwarding packets and Multicast traffic.
Hosts send IGMP reports to specify that they want to receive packets from
specific multicast groups. This results in the creation of an entry in the
Multicast filtering database.
MLD Snooping
Hosts use the MLD protocol to report their participation in Multicast
sessions, and the device uses MLD snooping to build Multicast membership
lists. It uses these lists to forward Multicast packets only to ports where there
are host nodes that are members of the Multicast groups. The device does not
support MLD Querier.
Hosts use the MLD protocol to report their participation in Multicast
sessions.
The device supports two versions of MLD snooping: