Simulation Intermediate

Network simulation brings your digital twin to life, allowing you to verify protocol behavior, trace packet paths, test access control lists, and measure performance under various conditions.

Simulation Approaches

Approach	Tools	Best For	Resource Cost
Config Analysis	Batfish	Routing verification, ACL testing, compliance	Low (CPU only)
Emulation	GNS3, EVE-NG, CML	Full protocol behavior, CLI testing	High (VMs per device)
Packet Simulation	ns-3, custom engines	Performance testing, capacity modeling	Medium
AI-Based Prediction	Custom ML models	Fast approximation, large-scale scenarios	Low (inference only)

Batfish for Configuration Analysis

Python

from pybatfish.client.commands import *
from pybatfish.question.bfq import *

# Initialize Batfish with your network snapshot
bf_init_snapshot('./network-configs', name='production')

# Trace a path from source to destination
result = bfq.traceroute(
    startLocation='@enter(core-rtr-01[GigabitEthernet0/0])',
    headers=HeaderConstraints(dstIps='10.0.50.100')
).answer()

# Check for undefined references in configs
issues = bfq.undefinedReferences().answer()

# Verify ACL behavior
acl_result = bfq.searchFilters(
    headers=HeaderConstraints(srcIps='10.0.0.0/8', dstPorts='22'),
    action='permit'
).answer()

Integrating Simulation into CI/CD

Run network simulations automatically when configuration changes are proposed, just like running unit tests for application code. This catches issues before they reach production.

Simulation in CI/CD: Use Batfish in your GitOps pipeline to automatically validate every proposed network config change. If the simulation detects reachability issues or policy violations, block the merge.

Next Step

Learn how to run what-if scenarios to test changes and failure modes safely.

Next: What-If Analysis →

← Modeling What-If Analysis →