Network Topologies
Network topologies, architectures, and types
What you will learn
- Describe star, mesh, bus, and ring topologies.
- Explain why star is the most common topology in modern LANs.
- Tie each topology to its weakest single point of failure.
- Distinguish a network's physical topology from its logical one.
Topology describes a network's shape, and every shape forces a trade-off. What the exam actually measures isn't "what's this shape called" but "what's its weakest failure point, and is the extra cost to strengthen it worth it?"
Star vs. Full Mesh
| Star | Full Mesh | |
|---|---|---|
| Structure | Every device connects to one central point (a switch) | Every device connects directly to every other device |
| Weakest failure point | The central point — if it fails, the whole network goes down | No central point of failure — very high resilience |
| Cost and complexity | Low — number of cables = number of devices | Very high — grows as n(n-1)/2 cables |
| Common use | Typical LANs (offices, homes) | Critical core networks requiring maximum availability (WAN between data centers) |
Other topologies the exam mentions
| Bus | All devices share one common cable — a single failure takes down the whole network; rare in modern designs. |
|---|---|
| Ring | Each device connects only to its two neighbors in a closed loop — one broken link isolates part of the ring without backup paths. |
| Hybrid | Combining more than one topology in a single network — the most realistic case in larger networks. |
Common confusion
A network's physical topology (how cables actually run) can differ from its logical topology (how data actually behaves). Wi-Fi, for example, is physically star-shaped — each device connects to a central access point — but logically all devices share the same wireless medium, closer to bus-like behavior.
What matters on the exam
- Star = most common today; its failure point is the central switch.
- Full mesh = highest resilience and highest cost, not for everyday use.
Quick check
Answer in your head first, then reveal.
What is the weakest failure point in a star topology?Reveal the answer
The central point (the switch).
Which topology has the highest resilience but highest cost?Reveal the answer
Full mesh.
Why is bus topology less common in modern designs?Reveal the answer
Because a break in the single shared cable takes down the entire network at once.
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Sources
Used to verify the facts. The writing is original to Passuit.