In subnets where IGMP is configured, IGMP snooping manages multicast traffic at Layer 2 to dynamically forward multicast traffic to interfaces that want to receive the multicast traffic only. IGMP snooping, thus, helps reduce the broadcast traffic in the layer 2 network.
Router sends out periodic general IGMP queries. When the IGMP snooping is enabled, the switch will response the query and create the entry per subnet in the layer forwarding table for each layer 2 multicast group. Host which are interested in the multicast traffic send IGMP join request and are added to the forwarding table.
**Note**
IGMP snooping constrains traffic in MAC multicast groups 0100.5e00.0001 - 0100.5eff.ffff
Configuration
- In global configuration : ip igmp snooping vlan <vlan number>
Configure host statically
Command | Purpose |
|---|---|
Switch(config-if)# ip igmp snooping vlan vlan_ID static mac_address interface interface_num | Configures a host statically in the VLAN. |
Show the multicast MAC address on the Switch
- Show MAC address of the multicast group and list of all ports which are associated with it.
Switch# show mac-address-table multicast vlan <Vlan number>
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