Generic mqtt interface to network server not working


Jan 21 12:23:51 vikram-VirtualBox chirpstack-network-server[5210]: time=“2020-01-21T12:23:51+05:30” level=error msg=“finished unary call with code Unknown” ctx_id=4ffb06ad-2c40-4e5d-b369-89127fdc1e8b error=“rpc error: code = Unknown desc = lorawan/band: invalid data-rate” grpc.code=Unknown grpc.method=SendProprietaryPayload grpc.service=ns.NetworkServerService grpc.start_time=“2020-01-21T12:23:51+05:30” grpc.time_ms=0.104 peer.address=“” span.kind=server system=grpc`

i am trying to link my network server to mqtt broker, but it does not work . here is the log , any idea how can i link my mqtt broker to network server. Currently i am running chirpstack on Ubuntu virtual machine