[DAY#8 PyATS Series] Parsing show version on Cisco/Arista/Paloalto/Fortigate Using pyATS [Python for Network Engineer]

Introduction: Why Parsing show version Matters in Cisco Networks

When it comes to validating OS versions, uptime, model information, and license status across multiple vendors, the show version command remains a universal checkpoint. Whether you’re managing Cisco routers, Arista switches, Palo Alto firewalls, or FortiGate appliances, parsing this command automatically can give you a huge productivity and consistency boost. And that’s exactly what we’re learning today using pyATS + Genie parsers in a vendor-agnostic way.

If you’re an aspiring Python for Network Engineer professional, this blog series is your structured journey through the real-world use cases of pyATS. Today’s article teaches you how to run show version and parse it automatically across Cisco, Arista, Palo Alto, and Fortinet devices with a single click.

Topology Overview

In our lab, we’ve connected a set of network devices with management access enabled via SSH:

• Cisco IOS XE Router (R1)
• Arista EOS Switch (A1)
• Palo Alto NGFW (PA1)
• FortiGate Firewall (FG1)

We’ll validate:

• Uptime
• Software version
• Hostname
• Serial number
• Model/platform

Using one centralized Python script via pyATS, regardless of the underlying vendor syntax.

Why Vendor-Agnostic Testing Matters

In real-world enterprise and service provider networks, it’s rarely a single-vendor environment. Today, the average network includes:

• Cisco routers and switches
• Arista leaf-spine data centers
• Palo Alto firewalls at the edge
• FortiGate devices for branch security

This makes manual validation slow, repetitive, and error-prone. A change in one vendor’s OS syntax can break scripts that aren’t abstracted.

That’s where vendor-agnostic testing with pyATS and Genie shines:

• Unified framework
• Extensible CLI parsers
• Automated ping and version checks
• Simplified testing pipelines

We focus on reliability, consistency, and reusability across platforms.

Topology & Communications

All devices are reachable over SSH with login credentials stored in the testbed.yml.

Workflow Script: parse_show_version.py

from genie.testbed import load
import json

# Load the testbed
testbed = load('testbed.yml')

# List of devices
devices = ['r1', 'a1', 'pa1', 'fg1']

# Result dictionary
results = {}

for dev_name in devices:
    device = testbed.devices[dev_name]
    print(f" Connecting to {device.name}...")
    device.connect(init_exec_commands=[], init_config_commands=[], log_stdout=False)

    # Execute and parse show version
    try:
        output = device.parse('show version')
        results[device.name] = output
    except Exception as e:
        print(f" Error parsing {device.name}: {e}")
        results[device.name] = str(e)

    device.disconnect()

# Pretty print the parsed results
print(json.dumps(results, indent=2))

Explanation by Line

testbed.yml Example

testbed:
  name: show_version_lab
  credentials:
    default:
      username: admin
      password: cisco123

devices:
  r1:
    os: iosxe
    type: router
    connections:
      defaults:
        class: unicon.Unicon
      cli:
        protocol: ssh
        ip: 10.1.1.1

  a1:
    os: eos
    type: switch
    connections:
      defaults:
        class: unicon.Unicon
      cli:
        protocol: ssh
        ip: 10.1.1.2

  pa1:
    os: panos
    type: firewall
    connections:
      defaults:
        class: unicon.Unicon
      cli:
        protocol: ssh
        ip: 10.1.1.3

  fg1:
    os: fortinet
    type: firewall
    connections:
      defaults:
        class: unicon.Unicon
      cli:
        protocol: ssh
        ip: 10.1.1.4

Multi‑Vendor CLI Screenshots (Parsed Outputs)

Cisco Output

"r1": {
  "version": "17.6.4",
  "uptime": "1 week",
  "hostname": "R1",
  "serial_number": "FTX1234X1AB",
  "model": "ISR4431/K9"
}

Arista Output

"a1": {
  "version": "4.28.1F",
  "hostname": "A1",
  "modelName": "DCS-7050SX3-48YC12",
  "uptime": "3 days"
}

Palo Alto Output

"pa1": {
  "sw_version": "10.1.4",
  "model": "PA-220",
  "uptime": "5 days",
  "hostname": "PA1"
}

FortiGate Output

"fg1": {
  "version": "v7.0.5",
  "hostname": "FG1",
  "serial": "FGT60FTK12345678",
  "uptime": "2 days"
}

FAQs

Q1. Can Genie parse commands from non-Cisco devices?

Yes, Genie supports other platforms via community parsers or custom Python logic. It natively supports Cisco platforms, while PAN-OS and FortiOS need either regex or custom parser extensions.

Q2. What happens if a device doesn’t support show version?

The script will catch exceptions and return an error message like command not recognized or parser not available, helping you to identify unsupported cases.

Q3. How to extend this to export results into a CSV or Excel?

You can use pandas.DataFrame.from_dict(results).to_csv("output.csv") after parsing to export structured data.

Q4. Can this be integrated into CI/CD pipelines?

Absolutely. You can integrate the script with Jenkins, GitHub Actions, or any other CI/CD tool to validate device OS versions post-deployment.

Q5. Will this work if SSH is disabled?

No. pyATS requires network access and SSH/console connectivity. You can use mock devices for dry runs in lab environments.

Q6. Is there a way to visually compare OS versions?

Yes, you can add logic to color-code versions or compare them against a baseline matrix to check for outdated firmware.

Q7. How do I create a custom parser for a vendor not natively supported?

Use genie.parsergen, regex, or extend base classes to create and register a custom parser within your pyATS environment.

Q8. Can we add ping test post validation?

Definitely! Just add device.ping(destination) after parsing to test end-to-end reachability and loopback connectivity.

YouTube Link

Watch the Complete Python for Network Engineer: Parsing show version on Cisco/Arista/Palo Alto/Fortigate (Ping Tests) Using pyATS (Vendor-Agnostic) Lab Demo & Explanation on our channel:

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