1

UCS Multicast• Support for IGMP Snooping

v1/v2/v3

• Pre UCSM 2.1, IGMP snooping cannot be disabled and querier functionality cannot be turned on.

• IGMP joins sent on Mrouter port

• Multicast packets are replicated at FI, IOM and Cisco VIC (if multiple vNICs present and are interested in a group)

FIFabric A

FIFabric B

Blade (VIC)

IOM

B

IOM

A

Chassis 1

Cluster

Rack Mount

VIC

N2232 N2232

Blade (VIC)

Mrouter

Port

2

Use Case for disabling IGMP Snooping• Disabling IGMP snooping will be necessary in few cases

like:- Certain applications do not rely on IGMP.- It can be used as a work-around when IGMP snooping

is not working as expected. Disable snooping and investigate all multicast traffic.

3

Use Case for querier functionality• In the absence of a querier, the IGMP entries on the FI

timeout after the initial join

• Multicast traffic with sender and receiver within UCS fails.

• Querier functionality is required on the upstream network which requires involvement from the network team.

4

Feature ImplementationEnd Host ModeIGMP Snooping Enabled / Querier Enabled• Will only send the queries to the hosts (blades). Will not send IGMP queries to

the upstream network

• The FIs don’t send the IGMP queries to the upstream switch as this contradicts the role of End Host mode in the network. This can lead to unwanted multicast traffic (both control and data) being sent to the FIs. This is the reason why it was decided to have EHM FIs be responsible for sending IGMP queries down to its blades only.

• As a result, require one of the following to be configured:1. Configure IGMP querier on upstream switch with IGMP snooping enabled; or

2. Disable IGMP snooping on upstream switch to flood mcast traffic; or

3. Alternatively, change the FIs to switch mode

5

Feature Implementation (Contd.)End Host ModeIGMP Snooping Enabled / Querier Disabled• Default mode, same as pre Del Mar release

• Requires either:1. IGMP Querier in the upstream switch for the VLAN with IGMP snooping enabled; or

2. Multicast router in the VLAN

IGMP Snooping Disabled / IGMP Querier Disabled• FIs will flood multicast traffic in the VLAN

• Requires one of the following to work successfully:1. Upstream switch can have IGMP snooping enabled or

2. Alternatively have it disabled on the upstream switchto flood mcast traffic

IGMP Snooping Disabled / IGMP Querier Enabled• This is not a valid configuration and is blocked by UCSM