Automating Network Tasks with Python

How I use Python to automate repetitive network configuration and monitoring tasks in my lab.

Why Automate

Configuring network devices manually works fine when you have two switches. When you have ten, or twenty, or a hundred, manual configuration becomes error-prone and time-consuming. Automation ensures consistency, saves time, and reduces human error.

In my lab, I use Python to automate configuration backups, monitoring checks, and bulk configuration changes.

Netmiko for Device Access

Netmiko is a Python library that simplifies SSH connections to network devices. It handles the quirks of different vendors (Cisco, Fortinet, Juniper, etc.) and provides a clean interface for sending commands and receiving output.

from netmiko import ConnectHandler

device = {
    "device_type": "cisco_ios",
    "host": "10.0.10.2",
    "username": "admin",
    "password": "securepassword",
}

connection = ConnectHandler(**device)
output = connection.send_command("show running-config")
connection.disconnect()

with open("switch_backup.txt", "w") as f:
    f.write(output)

This script connects to a Cisco switch, pulls the running configuration, and saves it to a file. I run it nightly on every network device to maintain configuration backups.

Paramiko for Custom SSH

For tasks where Netmiko's abstraction gets in the way, I use Paramiko directly. Paramiko is the SSH library that Netmiko is built on, and it gives you lower-level control over the SSH connection.

SNMP with PySNMP

For monitoring, I use PySNMP to query SNMP data from network devices. This lets me pull interface statistics, CPU usage, and environmental data programmatically.

from pysnmp.hlapi import *

iterator = getCmd(
    SnmpEngine(),
    CommunityData("public"),
    UdpTransportTarget(("10.0.10.2", 161)),
    ContextData(),
    ObjectType(ObjectIdentity("SNMPv2-MIB", "sysUpTime", 0))
)

errorIndication, errorStatus, errorIndex, varBinds = next(iterator)
for varBind in varBinds:
    print(f"{varBind[0]} = {varBind[1]}")

Practical Scripts

My most-used automation scripts:

1. Config backup: Connects to every network device and saves the running config. Runs nightly via cron.
2. Port audit: Checks which ports are up, which are down, and which have errors. Outputs a report.
3. VLAN audit: Pulls VLAN assignments from all switches and checks for inconsistencies.
4. Uptime check: Queries sysUpTime from all devices and flags any that have rebooted unexpectedly.

Each script is simple, focused, and reliable. They save me hours of manual checking every week.