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IGMP snooping on Cat3560

Hi,

In the following topology

R1(f0/0)------------(f0/1)SW1(f0/2)------------R2

R1 is configured as host (no ip routing) with ip igmp join 239.10.10.10 on fa0/0 and R2 with ip pim sparse-mode on f0/0. SW1 is a Catalyst 3560 running IOS 12.2(25)SEE4 working at Layer 2 only in this topology (VLAN 1).

I configured SW1 for igmp snooping:

ip igmp snooping

ip igmp snooping vlan 1

Basically, I can see 'snooped' muticast group (via IGMP reports sent by R1)

SW1#sh ip igmp snooping group

Vlan      Group             Type        Version     Port List

----------------------------------------------------------------

1         224.0.1.40        igmp        v2          Fa0/2

1         239.10.10.10      igmp        v2          Fa0/1, Fa0/2

SW1#

SW1#

SW1#

SW1#sh ip igmp snooping mrouter

Vlan    ports

----    -----

   1    Fa0/2(dynamic)

However CAM table doesn't have the entry for multicast group (Layer 2 GDA)

SW1#sh mac-address-table multicast

Vlan    Mac Address       Type       Ports

----    -----------       ----       -----

SW1#

I believe that it is not expected behavior.....Can you help me ?

Thanks.

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Hall of Fame Cisco Employee

IGMP snooping on Cat3560

Hello Carlo,

I believe I have stumbled across the same problem some time ago. According to the Configuration Guide for your IOS, this command is not supported although present in the CLI:

http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_25_see/configuration/guide/swuncli.html#wp1027528

The same document states you should use the show ip igmp snooping groups command to see the multicast groups, although that one will not display the multicast MAC addresses you were looking for.

The IOS you are using is fairly old. If this is a production switch, I would personally recommend upgrading to 12.2(55)SE6. Interestingly enough, however, the show mac address-table multicast command is not supported even in the latest 15.0 IOS. I guess after so many years (the IOS you're running was released sometime in 2008), Cisco software engineers could at least remove the unsupported command instead of leaving it in place - and confusing people.

Best regards,

Peter

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IGMP snooping on Cat3560

Just to completeness......I did a ping from R2 to 239.10.10.10 receiving echo replies sent by R1 but no (layer 2) multicast entry in CAM....

Someone can help me ?

Hall of Fame Cisco Employee

IGMP snooping on Cat3560

Hello Carlo,

I believe I have stumbled across the same problem some time ago. According to the Configuration Guide for your IOS, this command is not supported although present in the CLI:

http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_25_see/configuration/guide/swuncli.html#wp1027528

The same document states you should use the show ip igmp snooping groups command to see the multicast groups, although that one will not display the multicast MAC addresses you were looking for.

The IOS you are using is fairly old. If this is a production switch, I would personally recommend upgrading to 12.2(55)SE6. Interestingly enough, however, the show mac address-table multicast command is not supported even in the latest 15.0 IOS. I guess after so many years (the IOS you're running was released sometime in 2008), Cisco software engineers could at least remove the unsupported command instead of leaving it in place - and confusing people.

Best regards,

Peter

View solution in original post

IGMP snooping on Cat3560

Thanks !

Hall of Fame Cisco Employee

IGMP snooping on Cat3560

Hi Carlo,

You are welcome. Thank you!

Best regards,

Peter

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