Why Network Engineers Need Python

If you've been managing networks manually through CLI for years, you might wonder why everyone keeps talking about Python. The answer becomes crystal clear when you scale up: what works fine for 2-3 devices becomes a nightmare with 20, 50, or 200 devices.

The Problem with Manual Configuration

Let's say you need to configure VLAN 100 on 10 switches. The manual approach looks like this:

For each switch:

1. SSH to the device
2. Enter privileged mode
3. Type the same configuration commands
4. Save the configuration
5. Move to the next switch

Here's what you'd type for just one switch:

ssh [email protected]
Switch> enable
Switch# configure terminal
Switch(config)# vlan 100
Switch(config-vlan)# name SALES
Switch(config-vlan)# exit
Switch(config)# interface range fastethernet0/1-24
Switch(config-if-range)# switchport mode access
Switch(config-if-range)# switchport access vlan 100
Switch(config-if-range)# exit
Switch(config)# copy running-config startup-config

Now multiply this by 10 switches. That's roughly 30 minutes of typing the same commands over and over. And here's the kicker: human error is inevitable. Maybe you typo a VLAN number on switch #7, or forget to save the config on switch #3.

The Python Solution

With Python and a library like netmiko, you can configure all 10 switches in under 2 minutes with zero typos:

from netmiko import ConnectHandler

# List of switches to configure
switches = [
    '192.168.1.10', '192.168.1.11', '192.168.1.12',
    '192.168.1.13', '192.168.1.14', '192.168.1.15',
    '192.168.1.16', '192.168.1.17', '192.168.1.18', '192.168.1.19'
]

# Configuration commands
config_commands = [
    'vlan 100',
    'name SALES',
    'exit',
    'interface range fastethernet0/1-24',
    'switchport mode access',
    'switchport access vlan 100'
]

# Configure each switch
for switch_ip in switches:
    device = {
        'device_type': 'cisco_ios',
        'host': switch_ip,
        'username': 'admin',
        'password': 'your_password'
    }
    
    connection = ConnectHandler(**device)
    output = connection.send_config_set(config_commands)
    connection.save_config()
    connection.disconnect()
    
    print(f"Configured {switch_ip} successfully")

Run this script once, and all 10 switches are configured identically. No typos. No forgotten commands. No late nights fixing inconsistent configurations.

Beyond Time Savings

Python automation isn't just about speed—it's about reliability and scalability. When you automate network tasks, you get:

• Consistency: Every device gets exactly the same configuration
• Documentation: Your script becomes a living documentation of what was configured
• Auditability: You can easily see what changed and when
• Rollback capability: Store configurations before changes for easy rollback

More importantly, as your network grows to hundreds or thousands of devices, Python scales with you. The same script that configures 10 switches can configure 1,000 switches; it just takes a bit longer to run.

Getting Started

You don't need to become a software developer overnight. Start small:

1. Install Python and netmiko: pip install netmiko
2. Begin with simple tasks like collecting show command output
3. Gradually work up to configuration changes
4. Always test on lab equipment first

The learning curve is gentler than you might think, especially since you already understand networking concepts. You're just learning a new tool to implement them more efficiently.

What's Next

Ready to take the plunge? In our next post, we'll walk through setting up your Python environment and writing your first network automation script. We'll start with something simple but practical: collecting device information from multiple switches with just a few lines of code.