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Network architect

Make four decisions for a fictional office network and see how it copes when something fails. Then, if you like, reshape it and break it on purpose.

Time
About 6 minutes

Fictional data, run in your browser. It doesn’t connect to, scan or change any real system, and nothing you choose is sent to exQ.

Illustrative simulation

Step 1 of 4

Try it in a minute

A fictional office of about 30 people. Four decisions shape whether its network keeps working when something goes wrong.

The internet line goes down for the morning. What keeps the office online?

Want more? The full simulation has more settings, more scenarios and the reasoning behind every result.

Explore in more depth
Illustrative simulation
Simulate an event

Normal day: everyone has the internet and the server.

Traffic nowBackup, readyInstalled, not configuredFailedUntrusted trafficWi-Fi

Inspect a component

Select any component in the diagram to see what it does, what depends on it and what to check on site.

What this shows

What changed
Nothing has failed. Traffic flows up from the access switches, through the core switch and firewall, and out of line 1.
Why
Each layer has one job. Access switches connect desks and Wi-Fi; the core joins them; the firewall decides what passes between your networks and the internet.
Business impact
All 40 people have the internet and the server. 3 components would each take everyone offline if they failed; the overview below lists them.
Trade-offs
Choose an event to see how this design behaves when something breaks, then change the design and try again.

Who can reach what

  • Staff devices

    Office network

    InternetYes

    The serverYes

  • Guest devices

    Guest network

    InternetYes

    The serverNo, blocked by design

  • Cameras and printers

    Office network

    Plugged into access switch 2.

    InternetYes

    The serverYes, and it shouldn’t

  • Server or NAS

    Office network

    InternetYes

    The serverNot applicable

Your network overview

Built from the design above. It updates as you change it.

Network overview

About 40 people: 3 single points of failure for everyone

Illustrative

Topology

  • About 40 people (fictional), 2 access switches and 4 Wi-Fi access points.
  • One internet line; one firewall; one core switch.
  • An on-site server or NAS on the core.
  • Guest Wi-Fi on its own network.
  • One network for staff, servers and devices.

Single points of failure in this model

  • Line 1 takes everyone offline.
  • The firewall takes everyone offline.
  • The core switch takes everyone offline.
  • Access switch 1 takes the people connected to it offline.
  • Access switch 2 takes the people connected to it offline.

Segmentation

  • Guest Wi-Fi is its own network, with internet access only.
  • Staff devices, the server, cameras and printers share one network, so one compromised device can reach the rest.

Resilience considerations

  • Add a second internet line from a different provider, or a mobile backup.
  • With one firewall, keep a saved configuration and a fast-replacement support contract.
  • With one core switch, keep a spare and its saved configuration.
  • Put the cabinet on a UPS so the core and firewall ride through short power cuts. Power isn’t modelled here.
  • The server is one copy of its data: back it up somewhere else and test a restore.

Checks to make on site

  • Survey Wi-Fi coverage and interference before settling the number of access points.
  • Check each access switch’s PoE budget against the access points and phones it powers.
  • Trace and label every uplink and patch lead, and record them in a cabling schedule.
  • Confirm firmware and support status for the firewall and switches.
  • From a guest device, confirm the internet works and the server and staff devices can’t be reached.

Assumptions and limits

  • A fictional, simplified office: one building and one cabinet, with no power, voice system or cloud services modelled.
  • Redundant parts are assumed configured and tested. In a real network, that is exactly what needs checking.
  • Traffic between internal networks is routed through the firewall. Some designs route it at the core switch instead, with access lists.
  • This is a conceptual exercise, not a validated design. A real one starts with a survey of the building, the devices and how people work.

Generated in your browser from the choices above. It is an illustration, not an assessment, and nothing is sent to exQ.

What the network architect shows

Most office networks grow one cable and one router at a time. These are the ideas that decide whether a network shrugs off a fault or stops the whole office.

  • Traffic flows up, then out

    A laptop’s request travels through its access switch to the core switch, through the firewall and out of an internet line. Everything on that route is something the request depends on; anything with no alternative is a single point of failure.

  • Single points of failure are normal, if they’re known

    Small offices often accept one firewall or one core switch. That can be a sensible trade-off, as long as there is a spare, a saved configuration and a support contract that matches how long the business can be offline.

  • A backup that isn’t configured isn’t a backup

    A second internet line does nothing until the firewall is set to fail over to it, and nobody knows it works until someone tests it. The same goes for firewall pairs and second core switches: redundancy has to be configured, monitored and tested.

  • Segmentation decides how far a problem spreads

    On a flat network, a visitor’s laptop or a compromised camera can reach every device and the server, and that traffic never passes the firewall. Separate networks (VLANs) with firewall rules between them contain it, at the cost of more rules to plan and document.

  • Access points live and die with their switch

    Wi-Fi access points usually take their power over the network cable (PoE). When an access switch fails, the Wi-Fi in its part of the office goes with it, which is why a failed switch can look like a Wi-Fi problem.

  • What a real design adds

    This model leaves out power, cabling routes, voice systems, wireless interference and the building itself. A real design starts with a survey, an inventory of devices and how people work, and ends with documentation: a cabling schedule, an addressing plan and a record of every rule.

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