Quick Reference Guide

PowerConnect B-Series TI24X Configuration Guide 445
53-1002269-02
Configuring IGMP snooping
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NOTE
Use the passive mode of IGMP snooping instead of the active mode. The passive mode
assumes that a router is sending group membership queries as well as join and prune
messages on behalf of receivers. The active mode configures the device to send group
membership queries.
• All the device ports connected to the source and receivers or routers must be in the same
port-based VLAN.
• The PIM SM snooping feature assumes that the group source and the device are in different
subnets and communicate through a router. The source must be in a different IP subnet than
the receivers. A PIM SM router sends PIM join and prune messages on behalf of a multicast
group receiver only when the router and the source are in different subnet. When the receiver
and source are in the same subnet, they do not need the router in order to find one another.
They find one another directly within the subnet.
The device forwards all IP multicast traffic by default. Once you enable IGMP snooping and
PIM SM traffic snooping, the device initially blocks all PIM SM traffic instead of forwarding it.
The device forwards PIM SM traffic to a receiver only when the device receives a join message
from the receiver. Consequently, if the source and the downstream router are in the same
subnet, and PIM SM traffic snooping is enabled, the device blocks the PIM SM traffic and
never starts forwarding the traffic. This is because the device never receives a join message
from the downstream router for the group. The downstream router and group find each other
without a join message because they are in the same subnet.
NOTE
If the “route-only” feature is enabled on a Layer 3 Switch, PIM SM traffic snooping will not be
supported.
Configuring IGMP snooping
Configuring IGMP snooping on a device consists of the following global, VLAN-specific, and
port-specific tasks:
Global tasks
Perform the following global tasks:
• “Configuring the IGMP V3 snooping software resource limits”
• “Enabling IGMP snooping globally on the device”
• “Configuring the global IGMP mode”
• “Configuring the global IGMP version”
• “Modifying the age interval for group membership entries”
• “Modifying the query interval (active IGMP snooping mode only)”
• “Modifying the maximum response time”
• “Configuring report control” (rate limiting)
• “Modifying the wait time before stopping traffic when receiving a leave message”
• “Modifying the multicast cache age time”
• “Enabling or disabling error and warning messages”