10  Export to the Real World

A simulation is useful when the design can leave it.

10.1 The Concept First

NetSim exports more than a picture:

  • Device config bundle (.zip): per-device setup.sh, nftables.conf and dnsmasq.conf.
  • Containerlab topology: a .clab.yml with Linux nodes and firewall rules.
  • Docker Compose: an approximate L2 topology.
  • SVG/PNG diagrams: documentation-grade topology images.
  • Printable HTML report: diagram, inventory, cabling, routing tables, DHCP/DNS and firewall rulesets.

The generated configs are validated in CI against the real nft and dnsmasq binaries. That is the bridge from the simulator to a real machine.

The export is not a promise that the real network will behave identically. It is a starting point that preserves the design.

10.2 Understanding Through a Building Plan

A building plan is not the building. It is the document a builder can follow.

The export is the plan. The real network is the building.

10.3 Discovering Exports with Your AI Partner

Exploration 1: Choose the Export

Ask which export fits the task.

A team wants to hand a firewall design to an engineer, run it in a lab,
and include it in a report. Which NetSim exports fit each task? Explain
the limits.

Different artefacts for different readers.

Exploration 2: Review the Config

Ask what to check before running it.

Here is a generated nftables.conf:
[paste it]

List the checks before applying it to a real host: interfaces, addresses,
default policy, rule order, NAT and rollback.

A generated config is a draft until reviewed.

Exploration 3: Compare Simulation and Reality

Ask what changes.

The simulated network works. The real containerlab deployment does not.
List the differences that could explain it: interface names, kernel
settings, L2 behaviour, image versions and timing.

The export removes typing, not thinking.

10.4 From Concept to Practice

An export record:

Artefact Reader Check
setup.sh Engineer Interfaces and routes
nftables.conf Firewall owner Policy and order
dnsmasq.conf Service owner Records and upstreams
.clab.yml Lab owner Images and links
Diagram/report Stakeholder Accuracy and scope

10.5 Build Task

Export one topology as a config bundle and a diagram. Review the firewall config before running anything.

10.6 Classroom Connection

The export is the assessment bridge. A student can show the design, the config and the report, not only a canvas.

10.7 Practice Exercises

Exercise 10.1 (Level 1). Name three export types. Exercise 10.2 (Level 2). Export a topology JSON. Exercise 10.3 (Level 3). Export a config bundle. Exercise 10.4 (Level 4). Review a generated nftables config. Exercise 10.5 (Level 5). Deploy a containerlab export and compare it with the simulation.

10.8 Chapter Summary

  • NetSim exports configs, containerlab, Compose, diagrams and reports.
  • The config bundle is the bridge to a real machine.
  • Generated configs need review.
  • The export preserves the design, not the behaviour guarantee.
  • Remove typing, not thinking.

10.9 Reflection

Before moving on, ensure you:

10.10 Your Learning Journal

  1. Which export was most useful?
  2. What did the config review catch?
  3. Where would reality differ?

10.11 Next Steps

The design is exported. The appendices collect the lab map and the check types.