Technical data

BLADE OS 5.1 Application Guide
186
 Chapter 13: IGMP BMD00136, November 2009
IGMP Relay
The G8000 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 G8000 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 G8000, 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 G8000 uses health checks to select the primary
Mrouter.
Configuration Guidelines
Consider the following guidelines when you configure IGMP Relay:
 IGMP Relay and IGMP Snooping are mutually exclusive—if you enable IGMP Relay, you
must turn off IGMP Snooping.
 Add the upstream Mrouter VLAN 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.
RS G8000 (config)# ip igmp relay vlan <VLAN number>
RS G8000 (config)# no ip igmp flood
RS G8000 (config)# ip igmp cpu