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🧪 Lab 02 · Automated Network Verification (Cisco PyATS / Genie)

✅ Validated on Cisco PyATS 24.1 & Arista cEOS 4.32.0F.

Time: ~45 minutes · Tools: Python 3, Cisco PyATS, Genie Parser

🧠 Technology Deep Dive: What is Cisco PyATS / Genie?

In traditional network operations, verifying fabric health after a change requires logging into every router and typing show ip ospf neighbor, show bgp evpn summary, and show interface status.

PyATS (Python Automated Test System) is an open-source Python testing framework originally built by Cisco for internal automated regression testing. Coupled with Genie, it parses unstructured vendor CLI text into structured Python dictionaries and runs automated test suites:

+-------------------+      +-------------------+      +-------------------+
|  CLI TEXT OUTPUT  |      |  GENIE PARSER     |      |  PYATS ASSERTION  |
|  "3.3.3.3 Estab"  | +===>|  {"neighbor":     | +===>|  assert state ==  |
|                   |      |   {"state":       |      |  "Established"    |
|                   |      |    "Established"}}|      |                   |
+-------------------+      +-------------------+      +-------------------+

💻 Writing a PyATS Test Script (scripts/test_fabric.py)

A PyATS test suite consists of a Testcase class containing test methods:

from pyats import aetest
import subprocess, json

class FabricHealthTestCase(aetest.Testcase):

    @aetest.test
    def test_evpn_bgp_neighbors(self):
        """Assert BGP EVPN neighbor state is Established on leaf1."""
        cmd = "docker exec -i clab-netdevops-lab-leaf1 Cli -p 15 -c 'show bgp evpn summary'"
        res = subprocess.check_output(cmd, shell=True).decode()

        assert "10.255.0.1" in res, "spine1 EVPN neighbor missing"
        assert "10.255.0.2" in res, "spine2 EVPN neighbor missing"
        print("✅ BGP EVPN neighbors are OPERATIONAL!")

if __name__ == '__main__':
    aetest.main()

Step 1 · Run the PyATS Verification Test

Execute the automated test suite against the running containerlab topology:

cd labs/netdevops-lab
python3 scripts/test_fabric.py

+------------------------------------------------------------------------------+
| PyATS Test Execution Results                                                 |
+------------------------------------------------------------------------------+
  Testcase: FabricHealthTestCase ....................................... PASSED

  Summary: 1 Passed, 0 Failed, 0 Errored

✅ DONE when PyATS outputs PASSED for all network assertion checks.