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What is smart multicast in Catalyst 3750 switches?

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Smart multicast is a new level of efficiency for converged networks.

The Cisco Catalyst 3750 series supports smart multicast, which has only one copy of the multicast in the stack interconnect, thereby conserving bandwidth.

With Cisco StackWise technology, the Cisco Catalyst 3750 series offers greater efficiency for multicast applications, such as video. Each data packet is put onto the backplane only once, which provides more effective support for more data streams. This provides superior quality of service across the stack and at wire speed.

Each data packet has a 24-byte header with an activity list for the packet as well as a QoS designator. The activity list specifies the port destination or destinations and what should be done with the packet.

In the case of multicast, the master switch identifies which of the ports should receive a copy of the packets and adds a destination index for each port. One copy of the packet is put on the stack interconnect. Each switch port that owns one of the destination index addresses then copies this packet.

This creates a much more efficient mechanism for the stack to receive and manage multicast information.

For more information on  Frequently asked questions on 3750, refer to Cisco Catalyst 3750 Q&A.

For more information on Comparison of Normal Multicast in Stackable Switches and Smart Multicast in Cisco Catalyst 3750 Series Switches ,refer to Smart Unicast and Multicast One Packet, Many Destinations section of Cisco StackWise Technology section of Cisco StackWise Technology.

For additonal information on 3750 series switches, refer to Cisco Catalyst 3750 Data Sheet

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