Lenovo Flex System Fabric CN4093, Application Manual

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CN4093 Application Guide for N/OS 8.4
IGMP Relay
The CN4093 can act as an IGMP Relay (or IGMP Proxy) device that relays IGMP
multicast messages and traffic between an Mrouter and end stations. IGMP Relay
allows the CN4093 to participate in network multicasts with no configuration of
the various multicast routing protocols, so you can deploy it in the network with
minimal effort.
To an IGMP host connected to the CN4093, IGMP Relay appears to be an IGMP
multicast router (Mrouter). IGMP Relay sends Membership Queries to hosts,
which respond by sending an IGMP response message. A host can also send an
unsolicited Join message to the IGMP Relay.
To a multicast router, IGMP Relay appears as a host. The Mrouter sends IGMP host
queries to IGMP Relay, and IGMP Relay responds by forwarding IGMP host
reports and unsolicited join messages from its attached hosts.
IGMP Relay also forwards multicast traffic between the Mrouter and end stations,
similar to IGMP Snooping.
You can configure up to two Mrouters to use with IGMP Relay. One Mrouter acts
as the primary Mrouter, and one is the backup Mrouter. The CN4093 uses ICMP
health checks to determine if the primary and backup mrouters are reachable.
Configuration Guidelines
Consider the following guidelines when you configure IGMP Relay:
 IGMP Relay is supported in stand ‐ alone (non ‐ stacking) mode only.
 IGMP Relay and IGMP Snooping/Querier are mutually exclusive—if you enable
IGMP Relay, you must turn off IGMP Snooping/Querier.
 Add VLANs to the IGMP Relay list, using the following command:
 If IGMP hosts reside on different VLANs, you must:

Disable IGMP flooding.

Enable CPU forwarding to ensure that multicast data is forwarded across the
VLANs.
CN 4093(config)# ip igmp relay vlan
<VLAN ID>
CN 4093(config)# vlan
<VLAN ID>
CN 4093(config-vlan)# no flood
CN 4093(config)# vlan
<VLAN ID>
CN 4093(config-vlan)# cpu