CSM connection replication and IGMP snooping

Answered Question
Apr 13th, 2010
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Hi there,


I'm currently in the process of migrating from CSS  to CSM and I have a question regarding TCP state tracking between two CSM's.  In the documentation it says the the connection information is sent over to the secondary CSM using a multicast frame and that you must disable IGMP snooping for it to work properly.    I plan on utilizing multicast services off of the same 6500's the CSM's are installed and I'm wondering if disabling IGMP snooping will have a negative impact.  Can anyone comment?


Thanks in advance,


Brandon

Correct Answer by Sean Merrow about 6 years 11 months ago

Hi Brandon,


If you disable IGMP snooping globally, I would imagine it would cause problems.  However, you can disable IGMP snooping on a per-IP interface basis. If you execute the command "no ip igmp snooping" from within the submode "interface vlan ", this disables IGMP snooping only on the FT VLAN. This allows the CSM connection redundancy frames to pass without affecting IGMP snooping on other Cat6k VLANs.


It is recommended that this is the only command used in the FT VLAN interface. Don't assign an IP address to the FT VLAN interface or execute any other configuration command other than "no ip igmp snooping" on the FT VLAN interface. We intend the FT VLAN only to carry the CSM's specialized connection redundancy frames. It should not be used for any other purpose.


Hope this helps,

Sean

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Correct Answer
Sean Merrow Wed, 04/14/2010 - 11:12
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Hi Brandon,


If you disable IGMP snooping globally, I would imagine it would cause problems.  However, you can disable IGMP snooping on a per-IP interface basis. If you execute the command "no ip igmp snooping" from within the submode "interface vlan ", this disables IGMP snooping only on the FT VLAN. This allows the CSM connection redundancy frames to pass without affecting IGMP snooping on other Cat6k VLANs.


It is recommended that this is the only command used in the FT VLAN interface. Don't assign an IP address to the FT VLAN interface or execute any other configuration command other than "no ip igmp snooping" on the FT VLAN interface. We intend the FT VLAN only to carry the CSM's specialized connection redundancy frames. It should not be used for any other purpose.


Hope this helps,

Sean

thorsten.steffen Mon, 07/04/2011 - 05:44
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Hi Sean,

before deactivating igmp snooping the ft-vlan interface does not exist in the configuration.

After configuring the "no ip igmp snooping" command the interface it's still in shutdown state:

===

interface Vlan700

no ip address

no ip igmp snooping

shutdown

end

===


Is this the correct final configuration?


Best Regards

Thorsten

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