Wednesday, December 10, 2008

Multicast - IGMP Profile

Here is the topology for this lab:

R2 is the RP and will be sending multicast pings.
R3 is the PIM DR for the segment.
We will prevent R5 from joining group

To deny IGMP joins on a switch, we use the IGMP filter and profile commands.

First, create the profile:

SW1(config)#ip igmp profile 1

Then attach it to the port:

SW1(config)#int f0/5
SW1(config-if)#ip igmp filter 1

Now we can test by having R1 and R5 join a group in the range -

R1(config)#int e0/0
R1(config-if)#ip igmp join-group

R5(config)#int e0/0
R5(config-if)#ip igmp join-group

Let's debug on SW1 and see what happens:

SW1#debug ip igmp filter
event debugging is on

03:26:30: IGMPFILTER: igmp_filter_process_pkt(): checking group from Fa0/5: deny
03:26:31: IGMPFILTER: igmp_filter_process_pkt() checking group from Fa0/3 : no profile attached
03:26:33: IGMPFILTER: igmp_filter_process_pkt() checking group from Fa0/1 : no profile attached

No let's check R3 for any joined groups:

R3#show ip igmp groups
IGMP Connected Group Membership
Group Address Interface Uptime Expires Last Reporter Ethernet0/0 00:09:28 00:02:30 Ethernet0/1 00:29:57 00:02:09 Ethernet0/0 00:30:01 00:02:37

Just to make sure, we can verify that only R1 responds to pings:


Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to, timeout is 2 seconds:

Reply to request 0 from, 8 ms


  1. consise and helpfull,

  2. Brilliant LAB - thanks


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