Multicast on Layer 2 (Nexus)

[Felipe A. Amaya]

Hi Community experts,

I have been researching of a way if possible to allow multicast traffic on a layer two network in particular for an Oracle RAC, A Layer-2 VLAN is configured, the host have a private IP address of 192.168.x.x and they communicate with each other on this isolated broadcast domain but they have requested that we allow for multicast traffic.  

Is IGMP snooping the only feature that needs to be enable or am i totally lost.

Thank you in advance

[Dileep Sivadas Padmini]

Hi Felipe,

You may need to either disable IGMP snooping or configure IGMP querier IP for the VLAN.

Configure under vlan configuation.

Nexus(config)# vlan configuration XXX
Nexus(config-vlan-config))#ip igmp snooping querier X.X.X.X

or

Nexus(config)# vlan configuration XXX
Nexus(config-vlan-config))#no ip igmp snooping

Regards,
Dileep

[Felipe A. Amaya]

Thank you Dileep,

Do you have a link to the documentation by any chance, that may give me a broader understanding of the concept behind it.  

I will try that command on a device to see as well

Thanks in advance,

[Dileep Sivadas Padmini]

see below nexus 5K IGMP snooping section
https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/configuration/guide/cli/CLIConfigurationGuide/IGMPSnooping.html

Please the explanation for the terms.

IGMP Snooping

"The IGMP snooping software examines IGMP protocol messages within a VLAN to discover which interfaces are connected to hosts or other devices interested in receiving this traffic. Using the interface information, IGMP snooping can reduce bandwidth consumption in a multi-access LAN environment to avoid flooding the entire VLAN"

IGMP snooping enabled by default , so by disabling IGMP snooping, multicast will flood entire VLAN.

IGMP Snooping Querier

"When there is no multicast router in the VLAN to originate the queries, you must configure an IGMP snooping querier to send membership queries."

When there is no L3 interface configured in the VLAN, you need to configure IGMP querier IP address that enable switch to send IGMP queries messages to adjacent switches.

Regards,
Dileep

[Sergiu.Daniluk]

Hi Felipe,

I would recommend you to start by learning about IGMP, consolidating the fundamentals and with focus on the following:

• what is an IGMP querier
• how the receivers are announcing their intent of receiving multicast data
• what type of IGMP version exist and what are the differences b/w them

Once you have a general understanding about these points, then you can move to IGMP snooping, and everything will make more sense what happens when you have it disabled or enabled, why you need a querier etc.

There are a lot of resources on internet about IGMP, but since we are talking about Nexus switches, you can read this ones as well:

IGMP:

https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/6-x/multicast/configuration/guide/b_Cisco_Nexus_9000_Series_NX-OS_Multicast_Routing_Configuration_Guide/b_Cisco_Nexus_9000_Series_NX-OS_Multicast_Routing_Configuration_Guide_chapt...

IGMP Snooping:

https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/6-x/multicast/configuration/guide/b_Cisco_Nexus_9000_Series_NX-OS_Multicast_Routing_Configuration_Guide/b_Cisco_Nexus_9000_Series_NX-OS_Multicast_Routing_Configuration_Guide_chapt...

Cheers,

Sergiu