Cisco Group Management Protocol (CGMP)

In this lesson, we will cover, one of the imporant IP Multicast Protocols, CGMP (Cisco Group Management Protocol). It is a Cisco proprietary Layer 2 protocol used for Layer 2 efficiency at Multicast Memberships. So, how does this protcols works?

 

Basically, whenever a host want to join a multicast group, it sends IGMP Join message to the target group. This message goes to the multicast router.

After getting this messsage, router send a CGMP Join message to the switch about this membership. Switch adds these records to the CAM Table.

 

After such records, whenever a multicast activity is done, these CAM table is used.

 

In the working mechanims of Cisco Group Management Protocol, switches only listens the Cisco Group Management Protocol messages coming from the router. With these messages, they manage the efficient group membership facilities.

 

Cisco Group Management Protocol needs to be configured on both Layer 2 switches and Layer 3 Routers.

 

We have learned the basic messages of this multicsat protocol. What about the configuration? Now, let’s show this CGMP Configuration with an example.

 

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Cisco CGMP Configuration Example

 

Cisco Group Management Protocol is another Multicast Host Membership protocol. It is a Cisco proprietary protocol. In this configuration lesson, we will see how to configure CMGP on Cisco Catalyst Switches.

 

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Enabling CGMP on Switch

 

To enable CGMP on Cisco Catalyst switch we can use “ip cgmp” command. By default Cisco Group Management Protocol is enabled. But with this command a Join Message is also created again.

 

Switch(config)# interface gigabitethernet 1/1/1
Switch(config-if)# ip cgmp
Switch(config-if)# end
Switch# copy running-config

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Enabling CGMP on Router

 

We will enable Cisco Group Management Protocol on Router also. We will do this under the interface towards the switch.

 

Router(config)# interface gigabitethernet 1/1/1
Router (config-if)# ip cgmp
Router (config-if)# end
Router # copy running-config

 

Verification

 

Cisco Group Management Protocol uses IGMP messages. So, we can use the below IGMP commands also for this protocol.

 

• show ip igmp groups
• show ip igmp interface
• show ip mroute

Here, we have covered one of the important IP Multicast protocols. This protocol is not widely used today, but as a multicast protocol, it is good to learn a different concept. It is similar to standard based IGMP Protocol.