Chapter 11: Multicast; Igmp Snooping - Cisco SPS208G User Manual

Multicast

IGMP Snooping

SPS208G/SPS224G4/SPS2024 Service Provider Switches User Guide
Multicasting is a broadcast technique used in real-time applications such as
videoconferencing and multimedia streaming. Multicast forwarding allows a single
packet to be forwarded to multiple destinations. Layer 2 Multicast service is
based on a Layer 2 switch receiving a single packet addressed to a specific
Multicast address. Multicast forwarding creates copies of the packet, and
transmits the packets to the relevant ports. The Internet Group Management
Protocol (IGMP) allows hosts to notify their local switch or router that they want to
receive transmissions assigned to a specific Multicast group.
Multicast forwarding enables transmitting packets from either a specific Multicast
group to a source, or from a non- specific source to a Multicast group.
The device supports IGMPv1and IGMPv2.
The device supports IGMPv1, IGMPv2, and IGMPv3.
The Multicast configuration options are as follows:
•
IGMP Snooping
•
IGMP Querier
•
Bridge Multicast
•
Bridge Multicast Forward All
When IGMP Snooping is enabled globally, all IGMP packets are forwarded to the
CPU. The CPU analyzes the incoming packets and determines:
•
Which ports want to join which Multicast groups.
•
Which ports have Multicast routers generating IGMP queries.
•
Which routing protocols are forwarding packets and Multicast traffic.
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