Queriers and Non-Queriers

An IGMP snooping-enabled RUCKUS ICX device can be configured as a querier (active) or non-querier (passive). An IGMP querier sends queries; a non-querier listens for IGMP queries and forwards them to the entire VLAN. VLANs can be independently configured to be queriers or non-queriers. If a VLAN has a connection to a PIM-enabled port on another router, the VLAN must be configured as a non-querier. When multiple IGMP snooping devices are connected together, and there is no connection to a PIM-enabled port, one of the devices must be configured as a querier. If multiple devices are configured as queriers, after these devices exchange queries, then all except the selected device stop sending queries. The device with the lowest address becomes the querier. Although the system will work when multiple devices are configured as queriers, RUCKUS recommends that only one device (preferably the one with the traffic source) is configured as a querier.

The non-queriers always forward multicast data traffic and IGMP messages to router ports which receive IGMP queries or PIM hellos. RUCKUS recommends that you configure the device with the data traffic source (server) as a querier. If a server is attached to a non-querier, the non-querier always forwards traffic to the querier regardless of whether there are any clients on the querier.

Note: In a topology of one or more connecting devices, at least one device must be configured as active. Otherwise, none of the devices can send out queries, and traffic cannot be forwarded to clients.
Parent topic: IGMP Snooping Overview