An MVRP-aware device can exchange VLAN configuration information with other MVRP-aware devices, prune unnecessary broadcast and unknown unicast traffic, and dynamically create and manage VLANs on the devices. These devices form a reachability tree that is a subset of an active topology. To avoid any information loop, the forwarding ports of base spanning tree form the active topology.
Note
It is not mandatory to enable any of the STP variants before configuring MVRP if the topology is already Layer 2 loop free where MVRP can still function effectively.MVRP on the device propagates the configured VLANs to all MVRP participants to declare it over their respective MVRP-enabled ports. The device initiates a join event information which is placed inside an MVRP data unit (MVRPDU). The MVRPDU is transmitted as untagged Ethernet frame and is sent out as an advertisement through all ports wherever a declaration is made. The advertisement is transmitted only when the port's spanning tree state is forwarding.
Similarly, if a VLAN is removed from a port, MVRP on the device propagates a leave event to all MVRP participants which removes the registration and declaration for the VLAN and then sends out a leave message over their respective MVRP enabled ports. The receiving node mimics this behavior and, through this method, the removal of the VLAN configuration is communicated to the entire topology.
VLAN registration occurs only on ports of intermediate nodes where the MVRP advertisement is received. Each registration acts as a pointer towards the source of the VLAN declaration. If the VLAN configuration on a device changes, MVRP automatically changes the VLAN configurations of the affected devices. Using VLAN pruning, MVRP avoids unnecessary flooding and provides solution for better resource utilization and bandwidth conservation.