[DAY#1 PyATS Series] What Is PyATS & Genie? Why Vendor‑Agnostic Testing? (Ping Tests) Using pyATS (Cisco/Arista/Paloalto/Fortigate) [Python for Network Engineer]

Introduction on the Key Points

Today we dive into pyATS & Genie, Cisco’s powerful testing framework, and explore why vendor‑agnostic testing is no longer a “nice‑to‑have” but an essential skill for every Python for Network Engineer professional.

In this article, you’ll learn:

• What pyATS & Genie are, and how they fit together.
• The value of vendor‑agnostic testing in heterogeneous environments.
• How to run simple ping tests across Cisco, Arista, Palo Alto, and FortiGate devices.
• A complete workflow script, YAML testbed file, CLI screenshots, and more.
• Pro tips on scaling your tests for hundreds of devices.

By the end, you’ll be ready to spin up your first multi‑vendor ping validation with a single Python script—setting the stage for end‑to‑end network testing that works on any platform.

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Topology Overview

To keep things focused, our lab topology is minimal yet representative of a real‑world stack:

Each device has:

• A management IP for SSH.
• A loopback interface that we’ll ping.
• The standard vendor OS: Cisco IOS‑XE, Arista EOS, Palo Alto PAN‑OS, FortiOS.

Our goal: SSH into each device, issue a ping to every other loopback, and report success or failure—all via pyATS & Genie.

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Why Vendor‑Agnostic Testing Matters

The Modern Network Reality

Today’s networks are polyglot: Cisco in the core, Arista in the data center, Palo Alto at the perimeter, and FortiGate at branches. Each platform has unique CLI syntax and management paradigms.

The Pitfalls of Device‑Specific Scripts

• Maintenance nightmare when syntax changes.
• Fragmented knowledge across teams.
• Slow rollout of new tests.

The pyATS Advantage

• Unified Python API for any vendor.
• Genie parsers extract structured data effortlessly.
• Testbed abstraction via a single testbed.yml.
• Scalability: From 4 devices to 400 in the same loop.

By testing “once for all,” you future‑proof your validation suite against vendor churn and configuration drift.

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Topology & Communications

Device	Management IP	Loopback0	OS
Cisco	192.168.100.10	10.0.0.1	IOS‑XE
Arista	192.168.100.20	10.0.0.2	EOS
Palo Alto	192.168.100.30	10.0.0.3	PAN‑OS
FortiGate	192.168.100.40	10.0.0.4	FortiOS

• SSH is our transport for all devices.
• Ping tests target loopback addresses.
• We’ll loop through each source and ping all other targets.

This schema ensures consistent reachability checks across our multi‑vendor stack.

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Workflow Script

Create a file named loopback_ping_test.py with the following content:

#!/usr/bin/env python3

from genie.testbed import load
from unicon.core.errors import ConnectionError

def main():
    testbed = load('testbed.yml')
    devices = list(testbed.devices.keys())
    loopbacks = { dev: testbed.devices[dev].custom.get('loopback') 
                  for dev in devices }

    for src in devices:
        device = testbed.devices[src]
        print(f"\n Connecting to {src} ({device.connections.cli.ip})...")
        try:
            device.connect()
            print(f" Connected to {src}")

            for dst in devices:
                if src == dst: continue
                ip = loopbacks[dst]
                cmd = build_ping_cmd(device.os, loopbacks[src], ip)
                print(f" Ping {ip} from {src}: {cmd}")
                result = device.execute(cmd)
                print(result)

            device.disconnect()
            print(f" Disconnected from {src}")

        except ConnectionError as e:
            print(f" Connection failed for {src}: {e}")

def build_ping_cmd(os, src_ip, dst_ip):
    if os == 'panos':
        return f"ping source {src_ip} host {dst_ip}"
    elif os == 'fortios':
        return f"execute ping {dst_ip}"
    else:
        return f"ping {dst_ip}"

if __name__ == "__main__":
    main()

Save and run with:

python3 loopback_ping_test.py

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Explanation by Line

Line(s)	Description
load('testbed.yml')	Loads devices and credentials from a YAML testbed file.
devices = list(testbed.devices.keys())	Retrieves all device labels.
loopbacks dict comprehension	Extracts loopback IPs defined under custom.loopback.
device.connect()	Establishes SSH session via Unicon.
build_ping_cmd(...)	Dynamically builds vendor‑specific ping commands.
device.execute(cmd)	Executes CLI command and returns raw output.
device.disconnect()	Gracefully closes the session.
ConnectionError handling	Catches SSH failures per device to avoid script crash.

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testbed.yml Example

Create testbed.yml:

testbed:
  name: multi-vendor-lab
  credentials:
    default:
      username: admin
      password: cisco123

devices:
  cisco:
    os: iosxe
    type: router
    connections:
      cli:
        protocol: ssh
        ip: 192.168.100.10
    custom:
      loopback: 10.0.0.1

  arista:
    os: eos
    type: switch
    connections:
      cli:
        protocol: ssh
        ip: 192.168.100.20
    custom:
      loopback: 10.0.0.2

  paloalto:
    os: panos
    type: firewall
    connections:
      cli:
        protocol: ssh
        ip: 192.168.100.30
    custom:
      loopback: 10.0.0.3

  fortigate:
    os: fortios
    type: firewall
    connections:
      cli:
        protocol: ssh
        ip: 192.168.100.40
    custom:
      loopback: 10.0.0.4

This file is the single source of truth for all your device definitions and custom parameters.

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Multi‑Vendor CLI Screenshots

Cisco IOS‑XE

R1#ping 10.0.0.2
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/3 ms

Arista EOS

arista01#ping 10.0.0.3
10.0.0.3 is alive

Palo Alto PAN‑OS

> ping source 10.0.0.3 host 10.0.0.4
64 bytes from 10.0.0.4: icmp_seq=0 time=0.225 ms

FortiGate FortiOS

FGT01 # execute ping 10.0.0.1
Reply from 10.0.0.1: bytes=56 seq=1 ttl=255 time=1.2 ms

These examples demonstrate consistent success across all platforms, confirming that our vendor‑agnostic script works as intended.

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FAQs – pyATS & Genie Ping Tests

1. What is pyATS and how does it help network engineers?

Answer:
pyATS (Python Automated Test System) is a powerful, Python-based test automation framework developed by Cisco. It helps network engineers validate, test, and automate their network operations across multi-vendor environments. With its modular design, pyATS simplifies creating reusable test scripts, collecting CLI outputs, and analyzing results—making it perfect for vendor-agnostic testing scenarios. It allows engineers to perform tasks like configuration validation, reachability tests, and pre/post-checks without being tied to a specific vendor’s tooling.

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2. What is Genie and how is it different from pyATS?

Answer:
Genie is a library built on top of pyATS that provides abstraction and parsing capabilities. While pyATS focuses on the automation engine and test execution, Genie offers predefined parsers, test libraries, and clean Python APIs to interact with device outputs. Think of pyATS as the automation core, and Genie as the library that makes parsing and interacting with device outputs more developer-friendly. When combined, they streamline the entire testing lifecycle—especially helpful in multi-vendor CLI environments.

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3. Why should I care about vendor-agnostic testing as a network engineer?

Answer:
Most modern enterprise networks are multi-vendor—you may find Cisco switches, Arista leaf/spine fabrics, Palo Alto firewalls, and FortiGate security appliances all in the same topology. Relying on vendor-specific tools introduces silos and reduces flexibility. Vendor-agnostic testing ensures consistency, repeatability, and scalability across the network, helping identify configuration drifts and reduce downtime. With tools like pyATS and Genie, you can validate ping reachability, interface status, and routing tables—regardless of vendor CLI format.

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4. Can I run ping tests across Cisco, Arista, Palo Alto, and Fortinet using pyATS?

Answer:
Yes! pyATS supports CLI-based interaction over SSH, so as long as the device supports SSH and responds to basic commands (like ping, show, etc.), you can script ping tests using vendor-agnostic methods. The key is defining your testbed YAML properly and using Connection APIs or Genie Learn functions to interact with each device. Parsing CLI outputs can vary slightly depending on the command syntax, but with Genie or regular expressions, multi-vendor ping tests become achievable.

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5. How do I set up a testbed file for multi-vendor SSH access in pyATS?

Answer:
A testbed.yaml is the foundation of pyATS. You define all your devices here, including their platform type (like iosxe, eos, panos, fortinet), IP address, SSH credentials, and connection parameters. It tells pyATS how to reach the devices and what drivers/parsers to use. For multi-vendor networks, it’s crucial to be accurate in specifying OS/platform fields and connection methods. A single YAML file can cover Cisco, Arista, Palo Alto, and FortiGate in the same script—streamlining automation across your network stack.

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6. Does pyATS require the devices to have NETCONF, RESTCONF, or APIs enabled?

Answer:
No, not necessarily. pyATS primarily interacts with devices over CLI via SSH, making it a good fit for brownfield networks that lack modern APIs. While NETCONF/RESTCONF support exists for advanced use cases, many network engineers begin with SSH-based CLI automation. This lowers the barrier to entry and enables you to start automating immediately using existing infrastructure without additional configuration on devices.

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7. What is the learning curve of pyATS & Genie for network engineers with basic Python skills?

Answer:
If you know basic Python—variables, loops, functions—you’re already well-equipped to start with pyATS and Genie. The framework is network-engineer friendly and has a clear learning path. Unlike traditional Python libraries meant for developers, pyATS uses terms like device.connect(), device.parse(), and device.execute() that make sense in a network context. This aligns with how engineers think, making automation more intuitive and accessible.

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8. Is pyATS free and open to the public or tied to Cisco hardware only?

Answer:
Yes, pyATS and Genie are open for public use and not limited to Cisco gear. Although Cisco developed pyATS and uses it internally for massive-scale testing, they released its core as an open framework to the community. This has led to a growing ecosystem of multi-vendor use cases, and you can automate testing for Arista, Palo Alto, Fortinet, Juniper, and other platforms using the same tooling—making it ideal for any Python for Network Engineer journey.

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YouTube Link

Watch the Complete Python for Network Engineer: What Is PyATS & Genie? Why Vendor‑Agnostic Testing? (Ping Tests) Using pyATS (Cisco/Arista/Paloalto/Fortigate) Lab Demo & Explanation on our channel:

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