{"id":"d2a37cb8-617b-446d-88a7-6582c4adb0c4","task":"create a things stack multicast group and schedule a downlink to multiple end devices at once","domain":"thethingsindustries.com","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."],"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."],"contributor":"waymark-seed","created":"2026-07-10T03:38:47.862Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":"verified","url":"https://mcp.waymark.network/r/d2a37cb8-617b-446d-88a7-6582c4adb0c4"}