Igmp Leave Timer Guidelines; Igmp Report Suppression; Igmp Snooping Querier Configuration Guidelines And Restrictions - Cisco Catalyst 2950 Software Configuration Manual

Understanding IGMP Snooping

IGMP Leave Timer Guidelines

Follows these guidelines when configuring the IGMP leave timer:
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IGMP Report Suppression

Note IGMP report suppression is supported only when the multicast query has IGMPv1 and IGMPv2 reports.
This feature is not supported when the query includes IGMPv3 reports.
The switch uses IGMP report suppression to forward only one IGMP report per multicast router query
to multicast devices. When IGMP router suppression is enabled (the default), the switch sends the first
IGMP report from all hosts for a group to all the multicast routers. The switch does not send the
remaining IGMP reports for the group to the multicast routers. This feature prevents duplicate reports
from being sent to the multicast devices.
If the multicast router query includes requests only for IGMPv1 and IGMPv2 reports, the switch
forwards only the first IGMPv1 or IGMPv2 report from all hosts for a group to all the multicast routers.
If the multicast router query also includes requests for IGMPv3 reports, the switch forwards all IGMPv1,
IGMPv2, and IGMPv3 reports for a group to the multicast devices.
If you disable IGMP report suppression, all IGMP reports are forwarded to the multicast routers.

IGMP Snooping Querier Configuration Guidelines and Restrictions

Follow these guidelines and restrictions when configuring the IGMP snooping querier on the
Catalyst 2955 switches:
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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
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You can configure the leave time globally or on a per-VLAN basis.
Configuring the leave time on a VLAN overrides the global setting.
The default leave time is 1000 milliseconds.
The IGMP configurable leave time is only supported on hosts running IGMP Version 2.
The actual leave latency in the network is usually the configured leave time. However, the leave time
might vary around the configured time, depending on real-time CPU load conditions, network delays
and the amount of traffic sent through the interface.
The IGMP snooping querier is disabled by default.
Configure the VLAN in global configuration mode.
Configure an IP address on the VLAN interface. When enabled, the IGMP snooping querier uses the
IP address as the query source address.
If there is no IP address configured on the VLAN interface, the IGMP snooping querier tries to use
the configured global IP address for the IGMP querier. If there is no global IP address specified, the
IGMP querier tries to use the VLAN switch virtual interface (SVI) IP address (if one exists). If there
is no SVI IP address, the switch uses the first available IP address configured on the switch. The first
IP address available can be seen in the output of the show ip interface privileged EXEC command.
The IGMP snooping querier does not generate an IGMP general query if it cannot find an available
IP address on the switch.
The IGMP snooping querier supports IGMP Versions 1 and 2.
Chapter 20 Configuring IGMP Snooping and MVR
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