IGMP Snooping

How to configure IGMP Snooping on Layer 3 switches

The purpose Internet Group Management Protocol (IGMP) snooping is to restrain multicast traffic in a switched network. By default, a LAN switch floods multicast traffic within the broadcast domain and this can consume a lot of bandwidth if many multicast servers are sending streams to the segment.

Multicast IP addresses are Class D IP addresses. Therefore, all IP addresses from to are multicast IP addresses.

IGMP Snooping can be very effective in network environments where Multicast applications like Video/Audio streaming are being used.




CONFIGURATION - Management IP address and IGMP

Set the Management IP address

1) Plugged the console cable to the Serial port of the switch and the serial port on the PC

2) Open a new Hyper Terminal session (connecting via the COM port) - settings 9600, 8 , None , 1, None

3) Power Cycle the switch

4) Upon POST the User: prompt will appear

5) Username is admin , password "blank"

6) Type Enable to access the privileged mode (password "blank" )

7) Type network protocol none to reset the network settings

8) Type network parms <<Management IP>> <<Subnet Mask>> <<Default Gateway IP>>. For example network parms

9) User copy system:running-config nvram:startup-config to save the configuration

10) Check with show network if the settings are correct

The switch should now be accessible patching a CAT5 Straight-through cable. The PC NIC must be configured with an IP address within the same subnet used to configure the management IP of the switch (Example:

IGMP snooping implementation

Enable IGMP Snooping (CLI) on VLAN 1

(GSM7312)# config

(GSM7312) (config) #ip igmpsnooping

(GSM7312) (config) #ip igmpsnooping unknown-multicast filter

(GSM7312) (config) #ip igmpsnooping interfacemode

(GSM7312) (config) #exit

(GSM7312)# vlan database

This command activate IGMP on all the ports in VLAN 1

(GSM7312) (vlan) #ip igmp 1

This command activate the Querier to be the VLAN address (In this case

(GSM7312) (vlan) #ip igmpsnooping querier 1

(GSM7312) (vlan) #exit

Enable IGMP snooping on any VLAN

In order to activate IGMP on any other VLAN the following list of commands must be modified replacing <VLAN-ID> with the VLANID number:

GSM7312)# vlan database

(GSM7312) (vlan) #ip igmp <VLAN-ID>

(GSM7312) (vlan) #ip igmpsnooping querier <VLAN-ID>

(GSM7312) (vlan) #exit


Further information can be found here.


Document Type:

Documentation > Application Notes
Published 05/15/2009 05:56 AM   |   Updated 05/02/2012 09:58 AM


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