Configuring Igmp Snooping; Default Igmp Snooping Configuration; Enabling Or Disabling Igmp Snooping - Cisco Catalyst 2950 Software Configuration Manual

Chapter 16 Configuring IGMP Snooping and MVR
You should use the Immediate-Leave processing feature only on VLANs where only one host is
Note
connected to each port. If Immediate-Leave is enabled on VLANs where more than one host is connected
to a port, some hosts might be inadvertently dropped. Immediate Leave is supported only with IGMP
version 2 hosts.

Configuring IGMP Snooping

IGMP snooping allows switches to examine IGMP packets and make forwarding decisions based on their
content. To enable IGMP snooping on the switch to discover external multicast routers, the Layer 3
interfaces on the routers in the VLAN must already have been configured for multicast routing.
These sections describe how to configure IGMP snooping:
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Default IGMP Snooping Configuration

Table 16-3
Table 16-3 Default IGMP Snooping Configuration
Feature
IGMP snooping
Multicast routers
Multicast router learning (snooping) method
IGMP snooping Immediate Leave
Static groups

Enabling or Disabling IGMP Snooping

By default, IGMP snooping is globally enabled on the switch. When globally enabled or disabled, it is
also enabled or disabled in all existing VLAN interfaces. By default, IGMP snooping is enabled on all
VLANs, but it can be enabled and disabled on a per-VLAN basis.
Global IGMP snooping overrides the VLAN IGMP snooping. If global snooping is disabled, you cannot
enable VLAN snooping. If global snooping is enabled, you can enable or disable VLAN snooping.
78-11380-04
Default IGMP Snooping Configuration, page 16-5
Enabling or Disabling IGMP Snooping, page 16-5
Setting the Snooping Method, page 16-6
Configuring a Multicast Router Port, page 16-7
Configuring a Host Statically to Join a Group, page 16-8
Enabling IGMP Immediate-Leave Processing, page 16-9
shows the default IGMP snooping configuration.
Default Setting
Enabled globally and per VLAN
None configured
PIM-DVMRP
Disabled
None configured
Catalyst 2950 Desktop Switch Software Configuration Guide
Configuring IGMP Snooping
16-5