Cisco IGMP Configuration Example

In this configuration example, we will configure Cisco Catalyst Switch for IGMP (Internet Group Management Protocol). As you know IGMP is used to manage host memberships to the multicast groups. This is done at the edge switch in the multicast network. So, we will do our configuration on this edge switch.

For our IGMP Configuration Example, we will use the below Multicast topology:

Here, we will do IGMP Configuration on Cisco Catalyst switch for the below jobs:

• Switch Multicast Group membership
• Changing IGMP version
• Configuring IGMP timers

Let’s start to configure our Catalyst Switch for IGMPv3.

Switch Multicast Group membership

Firstly, we will configure our Switch A as a member of different Multicast Groups. Here, we will use the groups, 227.7.7.7 and 229.9.9.9. To do this, we will use “ip igmp join-group group-address” command.

SwitchA# configure terminal
SwitchA(config)# interface gigabitethernet 1/1/1
SwitchA(config-if)# ip igmp join-group 227.7.7.7
SwitchA(config-if)# ip igmp join-group 229.9.9.9
SwitchA(config-if)# end
SwitchA# copy running-config startup-config

By the way, there are two methods to pull the Multicast traffic to the switch. These methods can be used with below commands :

• ip igmp join-group group-name
• ip igmp static-group group-name

In join group method that we used, the switch both accepts and forwards the packet. This prevent fast switching. To use fast switching, static-group command can be used. With this command, switch only does forwarding, not accepts the packets.

Changing IGMP Version

As you know, there are three versions of IGMP. The default one is IGMP version 2. We will change it as IGMPv3.

SwitchA(config)# interface gigabitethernet 1/1/1
SwitchA(config-if)# ip igmp version 3
SwitchA# copy running-config startup-config 

Configuring IGMP Timers

There are some important timers used with IGMP. We can adjust them for our network. Or we can, use the default values. These timers and the configuration commands are given below:

• IGMP Host-Query Message

SwitchA(config)# interface gigabitethernet 1/1/1
SwitchA(config-if)# ip igmp query-interval 100

• IGMP Query Timeout

SwitchA(config)# interface gigabitethernet 1/1/1
SwitchA(config-if)# ip igmp querier-timeout 150

• Maximum Query Response Time

SwitchA(config)# interface gigabitethernet 1/1/1
SwitchA(config-if)# ip igmp query-max-response-time 32

Verification of IGMP

There are vaious verificaion commands that we can use after IGMP Configuration. Some of the important ones are given below:

• show ip igmp groups
• show ip igmp interface 
• show ip igmp ssm-mapping
• show ip igmp static-group