MLD Querier

MLD Querier is similar to IGMP querier. A multicast query router communicates with hosts on a local network by sending MLD queries. This router periodically sends a general query message to each local network of the router. This is standard multicast behavior.

Note

Note

Queries are sent only if PIM is enabled globally and on the interface. PIM and snooping cannot be enabled at the same time.

Each VLAN using MLD multicast must have a router performing multicast queries. Networks with no stand-alone devices currently have no capability for implementing the pruning of multicast traffic. A dedicated querier must be available on the network.

There are several behavioral differences between a traditional query router and a switch or stack using the MLD Querier functionality. The following are the differences:

The querier version is determined by the received query version and establishes the interface operational version. By default, the interface operational version is MLDv1. If the interface operational version is downgraded from MLDv2 to MLDv1 (when operational version is MLDv2 and a MLDv1 query is received), then all MLDv2 listeners (registered by MLDv2 reports) are removed and all incoming MLDv2 reports are dropped.