# Create multicast groups to send a downlink payload to multiple devices
<a name="lorawan-multicast-groups"></a>

To send a downlink payload to multiple devices, create a multicast group. Using multicast, a source can send data to a single multicast address, which is then distributed to an entire group of recipient devices.

Devices in a multicast group share the same multicast address, session keys, and frame counter. By using the same session keys, devices in a multicast group can decrypt the message when a downlink transmission is initiated. A multicast group only supports downlink. It doesn't confirm whether the downlink payload has been received by the devices.

With AWS IoT Core for LoRaWAN's multicast groups, you can:
+ Filter your list of devices by using the device profile, RFRegion, or device class, and then add these devices to a multicast group.
+ Schedule and send one or more downlink payload messages to devices in a multicast group, within a 48-hour distribution window. 
+ Have devices temporarily switch to Class B or class C mode at the start of your multicast session for receiving the downlink message.
+ Monitor your multicast group setup and the state of its devices, and also troubleshoot any issues.
+ Use Firmware Updates-Over-The-Air (FUOTA) to securely deploy firmware updates to devices in a multicast group.

 The following video describes how AWS IoT Core for LoRaWAN multicast groups can be created and walks you through the process of adding a device to the group and schedule a downlink message to the group.

[![AWS Videos](http://img.youtube.com/vi/https://www.youtube.com/embed/LcCR-1eKX1w/0.jpg)](http://www.youtube.com/watch?v=https://www.youtube.com/embed/LcCR-1eKX1w)


The following shows how to create your multicast group and schedule a downlink message.

**Topics**
+ [Create multicast groups and add devices to the group](lorawan-create-multicast-groups.md)
+ [Choose participating gateways to receive multicast downlink messages](lorawan-multicast-choose-gateways.md)
+ [Monitor and troubleshoot your multicast groups](lorawan-multicast-status.md)
+ [Schedule a downlink message for your multicast group](lorawan-multicast-schedule-downlink.md)