Question

Your team deployed a model-driven telemetry (MDT) dial-out subscription from an IOS XE router to a Telegraf collector over gRPC. The router logs show the subscription is in a 'valid' state and the transport session is established, but the collector receives packets that it logs as 'unable to unmarshal metric' and stores no data points. The Telegraf gNMI/cisco_telemetry_mdt input plugin was configured expecting self-describing GPB (key-value) encoding. What is the most likely cause of the collector failing to decode the telemetry stream?

Accepted Answer

The subscription on the router is configured with 'encoding encode-kvgpb' while the collector expects compact GPB, or vice versa — the encoding negotiated on the wire does not match what the plugin decodes.

Answer

The sample-interval on the sensor-group is set too low, causing the collector to drop packets before decoding them.

Answer

The router's NETCONF datastore is locked, preventing the YANG model from being serialized into the telemetry payload.

Answer

The gRPC session is missing TLS certificates, which silently corrupts the protobuf payload during transport.