Coding Skill for a Network Engineer

Why a Network Engineer Should Code

4 min readMay 14, 2021

When it comes to coding, we network engineers always ask one question, is coding my cup of tea? When you can configure and manage complex routing why not try your hands on coding. What matters is your determination and how excited you are about it. So let’s start coding..

In the era of automation when everything is getting automated, turning blind towards coding is not an option anymore!

Learning coding is not that hard as we think. Just remember “with determination one can achieve anything.”

I am going to talk about why a network/system engineer should learn coding, followed by a small demonstration.

Target Audience: Networking/system folks who are already writing some sort of scripting or willing to learn coding in Python.

Why a network engineer should code

You can write better code if you have domain knowledge
Everything is getting automated
Workloads are moving to Cloud or Hybrid cloud
Infrastructure is code in Cloud
Most of the product vendors are providing API
Using configuration management tools efficiently requires scripting skill
Coding is a basic requirement for automation

Some Use Cases for Automation

Automate repetitive task

Access-lists(ACL) configuration on Firewall
NAT configuration
Virtual-server configuration and management on loadbalancer
WideIP configuration and management on Global traffic manager
SSL Management
Audit and compliance
DNS record management

Configuration management

Device configuration
Configuration Backup
Configuration restore

Automate troubleshooting

Executing multiple “Show commands” at once
Automate troubleshooting workflow
Correlation of incidents

Automate Compliance

Automated configuration check against baseline
Automate Audit and compliance workflow

Selecting a right language for coding

You can begin with a scripting language and slowly you can transform yourself to a full stack developer if you wish. A scripting language is often a simpler language, and easier to learn than other languages, but still can do many things.

What is scripting?

A script or scripting language is a computer language with a series of commands within a file that is capable of being executed without being compiled. E.g. Python , Shell Script, Perl, PHP
Scripting is basically writing code to automate a certain process in a specific environment
Scripts are usually short computer programs that do steps that could be done one at a time by a person
Scripts automates a job to make it easier and more reliable.

With my personal experience Python is easy to learn but you have choice to learn any language. Below is stats of usage of some of the scripting languages(source: Internet).

Python 37.1%
Bash/Shell scripts 27%
Perl 11.8%
PHP 8.4%
JavaScript 6.7%
Ruby 4.9%
Other 2.1%

Why Python

Easy to learn
Clear syntax and easy code
Built in data structures
Python supports modules and packages, which encourages program modularity and code reuse.
Python is an interpreted,object-oriented, high-level programming language
Since there is no compilation step, its easy to edit,debug and test in runtime and the edit-test-debug cycle is incredibly fast.
It offer more than 147,000 libraries

Common Mistakes which happens in beginning

Writing code based on assumptions
Lack of proper requirement gathering
Lack of flowchart/Pseudo code
Jumping on Hands-on mode
Copying and pasting the code; unsure of what it does
Doesn’t follow the best practices
Doesn’t know exception error meanings
Not meaningful naming the Class/Method/Function such as xyz

How to Start

Learn basic of python, there are plenty for free courses available for beginners . Area of focus for Network Automation in Python could be:

Data types in python
Variables
Expression and operators
String and String Slicing
List, dict, set
Statements
Loop and conditions
File handling (reading and writing csv files)
Paramiko or Netmiko Library for SSH to remote system
Ansible

Demonstration

Use-Case: Get BGP status from multiple routers. This might be useful when you are in a troubleshooting call.

Step1: Install python3 on your system

Step2: Install paramiko package

pip3 install paramiko

Step3: Define list of device IP address

Step4: Define command to be executed on device (“show bgp vpnv4 unicast all summary” in this case)

Step5: Define paramiko client

Step6: Send commands to device through paramiko

Step7: Parse output as per your requirement.

Sample Code:

# Import Paramiko and other required modules here

import paramiko
import time

command = 'show bgp vpnv4 unicast all summary'


def execute_command(username, password, device_ip):
    
    ssh = paramiko.SSHClient()
    ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
    ssh.connect(device_ip, port=22, username=username, password=password, timeout=10, look_for_keys=False,
                allow_agent=False)

    remote_conn = ssh.invoke_shell()
    print(f'***SSH session established to the device {device_ip}***')

    remote_conn.recv(999)  # To remove whatever is currently in the buffer.
    remote_conn.send(f'{command}\n')

    output = ''
    time.sleep(2)  # To handle delay in output.
    resp = remote_conn.recv(9999)  # Buffer size should be adjusted accordingly
    output += resp.decode('utf-8')  # Output is bytes encoded, you need to decode it

    ssh.close()  # Close SSH session

    return output


if __name__ == '__main__':

    username = ''  # Your username goes here
    password = ''  # Your username goes here

    device_list = ['10.10.10.1', '10.10.10.2']  # Your list of devices go here. These are dummy IPs for demonstration purpose

    for ip_add in device_list: #Iterate over each device IP in list
        output = execute_command(username, password, ip_add)
        print(output)

This is a simple script to start with. This script will ssh to the device and retrieve a command output. You can add exception handling and other advance python features to it.

Note: Take extra care when you execute configuration changes on device.

Stay happy and blessed!!!