Task 9 - Configure Remaining Interfaces with gNMI

In the previous task, we used NETCONF to configure the link between ceos-01 and srl-01. Now, we will configure the remaining links in our topology using gNMI (gRPC Network Management Interface). This task will move at a faster pace since you are now familiar with the OpenConfig modules.

We need to configure the following remaining links:

Link Device A Interface IP Device B Interface IP
2 ceos-01 Ethernet2 192.168.1.4/31 srl-02 ethernet-1/1 192.168.1.5/31
3 srl-01 ethernet-1/2.0 192.168.1.6/31 srl-02 ethernet-1/2.0 192.168.1.7/31`

First Approach: Read-Modify-Write (Technique 3)

In this step, we will use Technique 3: Read-Modify-Write. This involves retrieving an existing configuration, modifying it, and pushing it back to a different path or device.

I recommended that you review gNMi paths before proceeding as you will use them extensively in this task..

Get Existing Configuration

The easiest way to configure the interfaces is to get the configuration of the interface that we already completed:

gnmic --config srl-gnmic.yml get --path /interface[name=ethernet-1/1]/subinterface[index=0] -t config

[
  {
    "source": "srl-01:57400",
    "timestamp": 1772910234636631063,
    "time": "2026-03-07T19:03:54.636631063Z",
    "updates": [
      {
        "Path": "srl_nokia-interfaces:interface[name=ethernet-1/1]/subinterface[index=0]",
        "values": {
          "srl_nokia-interfaces:interface/subinterface": {
            "admin-state": "enable",
            "ipv4": {
              "address": [
                {
                  "ip-prefix": "192.168.1.3/31"
                }
              ],
              "admin-state": "enable"
            }
          }
        }
      }
    ]
  }
]

Do the same for the network instance:

gnmic --config srl-gnmic.yml get --path /network-instance[name=default] -t config

[
  {
    "source": "srl-01:57400",
    "timestamp": 1772910838388260967,
    "time": "2026-03-07T19:13:58.388260967Z",
    "updates": [
      {
        "Path": "srl_nokia-network-instance:network-instance[name=default]",
        "values": {
          "srl_nokia-network-instance:network-instance": {
            "description": "Default",
            "interface": [
              {
                "interface-ref": {
                  "interface": "ethernet-1/1",
                  "subinterface": 0
                },
                "name": "ethernet-1/1"
              }
            ]
          }
        }
      }
    ]
  }
]

Edit Configuration

Edit the updates list in the configuration to match the interfaces table above:

"Path": "srl_nokia-interfaces:interface[name=ethernet-1/1]/subinterface[index=0]",
"values": {
  "srl_nokia-interfaces:interface/subinterface": {
    "admin-state": "enable",
    "ipv4": {
      "address": [
        {
          "ip-prefix": "192.168.1.5/31"
        }
      ],
      "admin-state": "enable"
    }
  }
}

"Path": "srl_nokia-network-instance:network-instance[name=default]",
"values": {
  "srl_nokia-network-instance:network-instance": {
    "description": "Default",
    "interface": [
      {
        "interface-ref": {
          "interface": "ethernet-1/1",
          "subinterface": 0
        },
        "name": "ethernet-1/1"
      }
    ]
  }
}

Push Configuration using gnmic

The gnmic tool uses set operation to push the configuration. Let's configure the link between ceos-01 and srl-02, starting from srl-02

Note: Update vs. Replace
The gnmic set --update operation performs a merge at the specified path, preserving other siblings (like other subinterfaces on the same port). Using --replace would perform a "delete-and-insert" at that path, potentially wiping out existing configuration not included in your request.

We use the Path and values above mostly unchanged, but the path must conform to the gNMI format. Notice also the single quotes that surround the configuration object: 

gnmic --config srl-gnmic.yml -a srl-02 set \
--update-path /interface[name=ethernet-1/1]/subinterface[index=0] \
--update-value '{"admin-state": "enable","ipv4": {"address": [{"ip-prefix": "192.168.1.5/31"}],"admin-state": "enable"}}'

gnmic sends this update to the running configuration. The output confirms the success of the update:

{
  "source": "srl-02",
  "timestamp": 1772912676743318280,
  "time": "2026-03-07T19:44:36.74331828Z",
  "results": [
    {
      "operation": "UPDATE",
      "path": "interface[name=ethernet-1/1]/subinterface[index=0]"
    }
  ]
}

Repeat for binding the interface to the network instance:

gnmic --config srl-gnmic.yml -a srl-02 set \
--update-path /network-instance[name=default]  \
--update-value '{"description": "Default","interface": [{"interface-ref": {"interface": "ethernet-1/1","subinterface": 0},"name": "ethernet-1/1"}]}'

Verify with gnmi_tool.py

Now use the gnmic again verify that the configuration was applied correctly.

gnmic --config srl-gnmic.yml -a srl-02 get --path /interface[name=ethernet-1/1]/subinterface[index=0] -t config

You should see the JSON output reflecting the new IP address and interface state.

Second Approach: gnmic generate (Technique 4)

The previous technique is useful for small changes, but for new features, Technique 4: gnmic generate is often faster.

The gnmic tool is able to generate configuration payload based on the target YANG data module. The gnmic generate command takes the target's YANG modules as input and generates:

  • Paths in xpath or gNMI formats.
  • Configuration payloads that can be used as update or replace input files for the Set command.
  • A Set request file that can be used as a template with the Set command.

Use the next example to generate the configuration payload for the interface in cEOS and save it to a file. The default format will be YAML.

gnmic generate --file openconfig set-request --update /interfaces/interface/subinterfaces/ > ceos_request.yml

Unlike the previous technique, the command generate with subcommand set-request provides a configuration payload ready to upload after editing

You need to make the following change to the file ceos_request.yml

  • Update the path to include the interface name
  • Fill the missing values
  • Remove the quotes surrounding the boolean and integer values
  • Removed unneeded items

The file should look like this:

updates:
- path: /interfaces/interface[name=Ethernet2]/subinterfaces
  value:
    subinterface:
    - config:
        description: "To srl-02"
        enabled: true
        index: 0
      index: 0
      ipv4:
        addresses:
          address:
          - config:
              ip: "192.168.1.4"
              prefix-length: "31"
              type: PRIMARY
            ip: "192.168.1.4"
        config:
          enabled: true

The file includes these components:

  • updates: This is a list that contains one or more update entries. Each entry specifies a path and the value to set at that path.
  • path: This specifies the path to the configuration that is being updated. There are two paths.
  • value: This section contains the configuration details for the specified path.

To upload this configuration, we use the set command

gnmic --config ceos-gnmic.yml set --request-file ceos_request.yml

The result should confirm the success of the update.

{
  "source": "ceos-01:6030",
  "timestamp": 1772930223840040329,
  "time": "2026-03-08T00:37:03.840040329Z",
  "results": [
    {
      "operation": "UPDATE",
      "path": "interfaces/interface[name=Ethernet2]/subinterfaces"
    }
  ]
}

Using what you've learned, configure the third link between srl-01 and srl-02 on their respective ethernet-1/2 interfaces. Don't forget that on SR Linux, you also need to associate the subinterface with the network-instance default.

Summary

You have now successfully configured a multi-vendor network using two different model-driven protocols!