ChirpStack has support for creating multicast-groups to which devices can be assigned. When enqueueing a downlink payload for a multicast-group, ChirpStack will analyze which gateways must be used for broadcasting to cover the complete multicast-group. This means that potentially, a single multicast downlink payload will be emitted multiple times. To avoid collisions, ChirpStack will put a delay between multiple emissions.

Multicast can be used for the following device-classes:

  • Class-B
  • Class-C

The configuration of the multicast-groups at the device side happens out-of-band. This means that assigning a device to a device-group does not configure the device itself to be part of the multicast-group.