Junos EZNC (py-junos-eznc)

2.7.6 · active · verified Thu Apr 16

Junos EZNC is a Python library for automating Juniper Junos devices, simplifying network management tasks for non-programmers. It provides a high-level API to connect to devices, retrieve facts, execute commands, and manage configurations using NETCONF. The current version is 2.7.6, with releases occurring periodically to add features, fix bugs, and ensure compatibility with newer Python versions and underlying dependencies.

Common errors

```
ImportError: cannot import name 'Device' from 'jnpr.junos'
```
cause The Python environment does not have `junos-eznc` installed, or it's installed in a different environment, or the import path is incorrect.

fix Ensure `junos-eznc` is installed via `pip install junos-eznc` in your active virtual environment. Verify the import statement: `from jnpr.junos import Device`.
```
jnpr.junos.exception.ConnectError: Cannot connect to device: ('paramiko.ssh_exception.AuthenticationException', 'Authentication failed.')
```
cause Incorrect username or password, or SSH key authentication failed. This can also occur if the user lacks necessary permissions on the Junos device.

fix Double-check credentials (username/password, SSH key path). Ensure the user is configured for NETCONF access on the Junos device. Verify network connectivity to the device's SSH port (22).
```
ncclient.operations.rpc.RPCError: <rpc-error>
```
cause A NETCONF RPC call failed on the Junos device. This usually indicates a syntax error in the command sent, invalid configuration, or an operational issue on the device itself.

fix Examine the full RPC error message for details. This often includes `error-message` and `error-path`. Consult Junos documentation for the correct syntax of the command or configuration being applied.
```
AttributeError: 'Device' object has no attribute 'facts'
```
cause The `facts` attribute (or other operational attributes) is only available after a successful connection has been established using `dev.open()`.

fix Call `dev.open()` before attempting to access `dev.facts` or other device attributes. Ensure connection success by handling `ConnectError`.

Warnings

breaking Field names within some tables (e.g., `VlanTable`, `BfdSessionTable`) were changed in version 2.6.8. Existing scripts relying on old field names will break.
Fix: Review release notes for 2.6.8 and update your code to use the new field names (e.g., `vlan-name` instead of `name` for VlanTable, `client-name` for BfdSessionTable).
gotcha PyEZ connections must be explicitly opened (`dev.open()`) and closed (`dev.close()`) to release resources. Forgetting to close can lead to lingering sessions or resource exhaustion on the device/client.
Fix: Always use a `try...finally` block to ensure `dev.close()` is called, even if errors occur during the connection lifetime. Alternatively, consider using `with Device(...) as dev:` for automatic resource management if your PyEZ version supports it (check documentation).
gotcha Older versions of `junos-eznc` (prior to 2.7.6) may not fully support Python 3.12+ due to underlying dependency changes or internal updates.
Fix: Ensure you are using `junos-eznc` version 2.7.6 or newer for official Python 3.12+ compatibility. Always check `requires_python` in `pyproject.toml` or PyPI.
deprecated The `look_for_keys` parameter for SSH authentication was introduced to control SSH agent usage. Older versions might not have this explicit control, defaulting to agent usage.
Fix: Upgrade to `junos-eznc` 2.6.7 or later to gain explicit control over `look_for_keys` parameter, allowing `True`/`False` to enable/disable SSH agent lookup.

Install

pip install junos-eznc Install latest version

Imports

Device
wrong:
```
import junos_eznc
```
correct:
```
from jnpr.junos import Device
```
The main Device object is located within the `jnpr.junos` namespace, not the top-level package.
ConnectError
```
from jnpr.junos.exception import ConnectError
```
Common exception for connection failures.

Quickstart

This quickstart demonstrates how to establish a connection to a Junos device, retrieve basic facts, and properly close the connection. It uses environment variables for credentials, making it safer for sharing. For production environments, `hostkey_verify` should be set to `True` for secure SSH connections.

import os
from jnpr.junos import Device
from jnpr.junos.exception import ConnectError

host = os.environ.get('JUNOS_HOST', 'your_junos_device_ip')
user = os.environ.get('JUNOS_USER', 'your_username')
password = os.environ.get('JUNOS_PASSWORD', 'your_password')

dev = None
try:
    # hostkey_verify=False for labs/quick starts, use True in production
    dev = Device(host=host, user=user, password=password, port=22, hostkey_verify=False)
    dev.open()
    print(f"Connected to device: {dev.hostname}")
    print(f"Device facts: {dev.facts['hostname']}, {dev.facts['version']}")
    # Example: Execute a command
    # rpc_resp = dev.rpc.get_system_uptime_information()
    # print(rpc_resp.find('.//up-time').text)

except ConnectError as err:
    print(f"Connection error: {err}")
except Exception as err:
    print(f"An error occurred: {err}")
finally:
    if dev and dev.connected:
        dev.close()
        print("Disconnected from device.")

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