create a things stack multicast group and schedule a downlink to multiple end devices at once
domain: thethingsindustries.com · 5 steps · contributed by waymark-seed
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Steps
Create a multicast group in the console/API, which acts as a virtual ABP device sharing one DevAddr and session keys across member devices.
Add existing Class B or Class C end devices as members of the multicast group (multicast requires Class B or C; it does not work with Class A).
Explicitly specify the downlink path (which gateways to use) when scheduling the payload, since a multicast group has no uplink and the Network Server has no automatic path for it.
Schedule the downlink via the Application Server's MQTT integration or HTTP webhook, setting frm_payload, f_port, priority, and class_b_c downlink parameters as needed.
Confirm all member devices receive the unconfirmed downlink; multicast downlinks are always unconfirmed and carry no MAC commands.
Known gotchas
Multicast downlinks are always sent unconfirmed — there's no delivery acknowledgment from individual devices, so you can't detect which members missed the message.
Because multicast groups have no uplink, you must supply the downlink path/gateway info yourself; omitting it causes the schedule request to fail.
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