Netmiko

Warnings

• breaking The exceptions module was relocated from `netmiko.ssh_exceptions` to `netmiko.exceptions`. Code relying on the old import path will break.
  Fix: Update import statements from `from netmiko.ssh_exceptions import ...` to `from netmiko.exceptions import ...`.
• breaking `send_command` and `send_command_timing` methods were refactored to primarily use the `read_timeout` argument. Older `delay_factor` based logic might behave differently, potentially causing unexpected timeouts or delays.
  Fix: Review code using `send_command` or `send_command_timing` and adjust `read_timeout` parameters as needed, understanding its direct impact on how long Netmiko waits for output. `delay_factor` is still available but `read_timeout` is preferred.
• breaking Support for older Python versions is periodically dropped. Python 3.7 support was dropped in v4.3.0, and Python 3.8 support was dropped in v4.5.0. Netmiko 4.6.0 requires Python >= 3.9.
  Fix: Ensure your Python environment is running version 3.9 or higher to use Netmiko 4.6.0+.
• gotcha While Netmiko includes `ntc-templates` (which uses `TextFSM`) for parsing, users often forget to enable structured output. By default, `send_command` returns raw string output. To get structured data for supported commands, you must use the `use_textfsm=True` argument.
  Fix: When calling `send_command`, add `use_textfsm=True` to automatically parse output using available NTC templates. Example: `net_connect.send_command('show ip int brief', use_textfsm=True)`.
• gotcha The `session_log` functionality, while intended to hide sensitive information like passwords, has had scenarios where it failed to do so. It should always be treated as a security-sensitive file and carefully managed.
  Fix: Carefully review `session_log` files for sensitive data before sharing. Consider limiting its use or implementing stricter log management practices like secure storage and access controls.
• gotcha Python 3.13 removed `telnetlib` from its standard library. Netmiko v4.4.0 vendorized `telnetlib` internally to maintain Telnet support. Users on older Netmiko versions (prior to 4.4.0) attempting to use Telnet with Python 3.13 would encounter import errors.
  Fix: Upgrade Netmiko to version 4.4.0 or newer if using Python 3.13 and requiring Telnet functionality.

Install

• pip install netmiko Install Netmiko

Imports

• ConnectHandler

  from netmiko import ConnectHandler

• NetmikoTimeoutException

  from netmiko.exceptions import NetmikoTimeoutException

  The exceptions module was moved in Netmiko 4.0.0.
• NetmikoAuthenticationException

  from netmiko.exceptions import NetmikoAuthenticationException

  The exceptions module was moved in Netmiko 4.0.0.

Quickstart

Connects to a network device using credentials from environment variables, sends a 'show ip int brief' command, and attempts to parse the output using TextFSM via `use_textfsm=True`. Remember to configure environment variables like NETMIKO_HOST, NETMIKO_USERNAME, NETMIKO_PASSWORD, and NETMIKO_DEVICE_TYPE before running.

import os
from netmiko import ConnectHandler
from netmiko.exceptions import NetmikoTimeoutException, NetmikoAuthenticationException

# Define device parameters using environment variables for security
device_ip = os.environ.get('NETMIKO_HOST', 'your_device_ip')
username = os.environ.get('NETMIKO_USERNAME', 'your_username')
password = os.environ.get('NETMIKO_PASSWORD', 'your_password')
device_type = os.environ.get('NETMIKO_DEVICE_TYPE', 'cisco_ios') # e.g., cisco_ios, juniper, arista_eos, etc.

if 'your_device_ip' in device_ip or not all([device_ip, username, password, device_type]):
    print("Please set NETMIKO_HOST, NETMIKO_USERNAME, NETMIKO_PASSWORD, and NETMIKO_DEVICE_TYPE environment variables, or update the placeholder values.")
    exit(1)

device = {
    "device_type": device_type,
    "host": device_ip,
    "username": username,
    "password": password,
    # "optional_args": {"port": 22}, # Example for custom SSH port
}

try:
    print(f"Connecting to {device_ip}...")
    with ConnectHandler(**device) as net_connect:
        print("Successfully connected!")
        # Use use_textfsm=True to attempt structured output parsing
        output = net_connect.send_command("show ip int brief", use_textfsm=True)
        print("\n--- Output of 'show ip int brief' (parsed with TextFSM) ---\n")
        print(output)

        # Example for sending configuration commands
        # config_commands = ["interface loopback 0", "ip address 1.1.1.1 255.255.255.255"]
        # output_config = net_connect.send_config_set(config_commands)
        # print("\n--- Configuration Output ---\n")
        # print(output_config)

        net_connect.disconnect()
        print("Disconnected.")

except NetmikoAuthenticationException:
    print("Authentication failed. Check username and password.")
except NetmikoTimeoutException:
    print("Connection timed out. Check host IP and network connectivity.")
except Exception as e:
    print(f"An unexpected error occurred: {e}")