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gNMI (gRPC Network Management Interface)

gRPC-based protocol for the modification and retrieval of configuration from a target device, as well as the control and generation of telemetry streams from a target device to a data collection system. The intention is that a single gRPC service definition can cover both configuration and telemetry - allowing a single implementation on the target, as well as a single NMS element to interact with the device via telemetry and configuration RPCs.

gNMI is gRPC Network Management Interface developed by Google. gNMI provides the mechanism to install, manipulate, and delete the configuration of network devices, and also to view operational data. The content provided through gNMI can be modeled using YANG. gRPC is a remote procedure call developed by Google for low-latency, scalable distributions with mobile clients communicating to a cloud server. gRPC carries gNMI, and providesthe meansto formulate and transmit data and operation requests. When a gNMI service failure occurs, the gNMI broker (GNMIB) will indicate an operational change of state from up to down, and all RPCs will return a service unavailable message until the database is up and running. Upon recovery, the GNMIB will indicate a change of operation state from down to up, and resume normal handling of RPCs

How does gNMI work?

The keynoperation of gnmi to retrieve data from the device

RPC Name Purpose Initiator
Get Retrieve current state/config data Client → Server
Set Change or update configuration Client → Server
Subscribe Receive live telemetry streams Client ↔ Server

gNMI Client: Usually a network controller, automation platform, or monitoring tool (e.g., OpenConfig collector, custom app).

gNMI Server: Runs on the network device (router, switch, etc.), exposing config and telemetry.

Example usage

Priya is a network automation engineer working with hundreds of routers in a cloud data center. She needs to monitor interface status and push new configurations quickly and reliably. Instead of using traditional CLI scripts, Priya leverages gNMI—a high-performance, model-driven protocol for managing devices at scale.

gNMI allows Priya to:

  • Retrieve configuration and operational data (GET).
  • Push configuration changes (SET).
  • Subscribe to real-time telemetry (SUBSCRIBE).
  • Use a single, secure, and efficient protocol for all tasks.

To query interface status on a Nokia SR Linux router, Priya uses the OpenConfig gNMI CLI tool:

1. Install gNMI CLI

bash -c "$(curl -sL https://get-gnmic.openconfig.net)"

2. SSH into the device and enable gnmi server

A:admin@srl# enter candidate

# 1) Enable the gNMI instance
set system grpc-server gnmi admin-state enable

# 2) Tell it which services to run (the ‘gnmi’ service)
set system grpc-server gnmi services [gnmi]

# 3) Bind it to port 57400
set system grpc-server gnmi port 57400

# 4) (Optional if you’ve already got a cert bound)  
#    Ensure it’s using the default self-signed profile
set system grpc-server gnmi tls-profile default-tls-profile

commit stay

3. Run a GET Request

gnmic -a 172.20.20.2:57401 \
      -u admin \
      -p NokiaSrl1! \
      --insecure \
      get --path /interface \
      --encoding ASCII

That gnmic command will connect to your Nokia SR Linux device at 172.20.20.2:57401 via gNMI, authenticate as admin with password NokiaSrl1!, and request data from the /interface path in the SR Linux YANG model.

Specifically:

  • get – means you’re requesting the current state/configuration data for that path.

  • --path /interface – targets the top-level interface container (from the srl_nokia-interfaces module).

  • --encoding ASCII – tells the device to return the result in ASCII text instead of JSON or Protobuf (basically a CLI-style representation).

Reference

gnmi