Configuring Igmp Snooping - HP A6600 Configuration Manual

Configuring IGMP snooping

Whenever mentioned in this document, a router port is a port on the switch that leads the switch to a
Layer 3 multicast device, rather than a port on a router.
Unless otherwise specified, router/member ports mentioned in this document include static and dynamic
ports.
An IGMP-snooping-enabled switch deems that all its ports on which IGMP general queries with the source
IP address other than 0.0.0.0 or PIM hello messages are received are dynamic router ports. For more
information about PIM hello messages, see
IGMP snooping is a multicast constraining mechanism that runs on Layer 2 devices to manage and
control multicast groups.
By analyzing received IGMP messages, a Layer 2 device running IGMP snooping establishes mappings
between ports and multicast MAC addresses, and forwards multicast data based on these mappings.
As shown in
to all devices at Layer 2. When IGMP snooping is running on the switch, multicast packets for known
multicast groups are multicast to the receivers, rather than broadcast to all hosts, at Layer 2.
Figure 11 Before and after IGMP snooping is enabled on the Layer 2 device
IGMP snooping forwards multicast data to only the receivers requiring the data at Layer 2. It brings the
following advantages:
• Reducing Layer 2 broadcast packets, thus saving network bandwidth.
• Enhancing the security of multicast traffic.
• Facilitating the implementation of per-host accounting.
Figure 11, when IGMP snooping is not running on the switch, multicast packets are flooded
"Configuring PIM."
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