892 PowerConnect B-Series FCX Configuration Guide53-1002266-01Overview27When any port of a VLAN is configured for MLDv2, the VLAN matches both source and group (S G)in hardware switching. If no port is configured for MLDv2, the VLAN matches group only (* G).Matching (S G) requires more hardware resources than (* G) when there are multiple serverssharing the same group. For example, two data streams from different sources to the same grouprequire two (S G) entries in MLDv2, compared to only one (* G) in MLDv1. Dell recommends thatyou use MLDv2 only in a source-specific application. Because each VLAN can be configured for theversion independently, some VLANs might match (* G) while others match (S G).To receive data traffic, MLD Snooping requires clients to send membership reports. If a client doesnot send reports, you must configure a static group to force traffic to client ports. The static groupcan either apply to some ports or to the entire VLAN.Configuring queriers and non-queriersAn MLD Snooping-enabled device can be configured as a querier (active) or non-querier (passive).An MLD querier sends queries; a non-querier listens for MLD queries and forwards them to theentire VLAN. VLANs can be independently configured as queriers or non-queriers. If a VLAN has aconnection to an IPv6 PIM-enabled port on another router, the VLAN should be configured as anon-querier. When multiple MLD snooping devices are connected together, and there is noconnection to an IPv6 PIM-enabled port, one of the devices should be configured as a querier. Ifmultiple devices are configured as queriers, after multiple devices exchange queries, then alldevices except the winner (the device with the lowest address) stop sending queries. Although thesystem works when multiple devices are configured as queriers, Dell recommends that only onedevice, preferably the one with the traffic source, is configured as the querier.Because non-queriers always forward multicast data traffic and MLD messages to router portswhich receive MLD queries or IPv6 PIM hellos, Dell recommends that you configure the deviceswith the data traffic source (server) as queriers. If a server is attached to a non-querier, thenon-querier always forwards traffic to the querier regardless of whether or not there are clients onthe querier.NOTEIn a topology with one or more connected devices, at least one device must be running PIM, orconfigured as active. Otherwise, no devices can send queries, and traffic cannot be forwarded toclients.VLAN specific configurationYou can configure MLD snooping on some VLANs or all VLANs. Each VLAN can be independentlyenabled or disabled for MLD snooping, or can be configured with MLDv1 or MLDv2. In general, theipv6 mld-snooping... commands apply globally to all VLANs except those configured withVLAN-specific mld-snooping... commands. VLAN-specific mld-snooping commands supersedeglobal ipv6 mld-snooping commands.Using MLDv1 with MLDv2MLD snooping can be configured as MLDv1 or MLDv2 on individual ports on a VLAN. An interfaceor router sends queries and reports that include the MLD version with which it has beenconfigured. The version configuration applies only to the sending of queries. The snooping devicerecognizes and processes MLDv1 and MLDv2 packets regardless of the version configured.
