What types of topologies exist?

Network topologies can be divided into classic (basic) ones and modern ones (used in large networks and data centers). Below are all the main types that are important to know for an interview.

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#Classic topologies

#1. "Bus" topology

All devices are connected to a single shared cable.

Pros:

• simple and cheap
• minimal cable usage

Cons:

• cable damage breaks the whole network
• many collisions
• almost never used today

Where it was used: old versions of Ethernet (10BASE2/5).

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#2. "Star" topology - the main topology of modern Ethernet

All nodes are connected to a central device - a switch (less often a hub).

Pros:

• a failure of one node does not affect the network
• easy to scale
• high performance

Cons:

• a failure of the central device → the network becomes unavailable

Where it is used: practically all home and office LANs.

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#3. "Ring" topology

Devices are connected in a chain forming a ring.

Pros:

• no collisions (Token Ring, FDDI)

Cons:

• a break in the ring causes problems
• difficult to upgrade

Where it was used: in old corporate networks.

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#4. "Fully connected" / "Mesh" topology

Each node is connected to several others. Can be:

• full mesh - every node with every other
• partial mesh - only important nodes have many connections

Pros:

• maximum fault tolerance
• high bandwidth

Cons:

• expensive
• hard to manage and scale

Where it is used: Wi-Fi Mesh systems, provider backbones.

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#5. "Tree" topology

A hierarchy of devices: root switch → distribution switches → access switches.

Pros:

• clear structure
• convenient for scaling

Cons:

• dependency on top-level equipment

Where it is used: the classic structure of corporate LANs.

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#Combined topologies

In practice, real networks almost always use mixed topologies, for example:

#Star-bus

several stars joined by a shared bus (looked like stars connected by hubs in the 90s).

#Star-ring

switching equipment forms a ring, while end stations form a star.

#Hybrid Mesh/Tree

modern networks of telecom operators.

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#Modern data center topologies (if you want to stand out in an interview)

#1. Clos topology

A hierarchical, multi-level mesh structure with equal paths between nodes.

#2. Fat-Tree

A variant of the tree, but with increased bandwidth at the upper levels.

#3. Spine-Leaf

A two-level topology:

• Leaf - switches that servers connect to
• Spine - core switches

Every Leaf is connected to every Spine.

This is the standard in modern data centers.

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#How to answer correctly in an interview

There are several types of topologies: bus, star, ring, tree, and mesh. In practice, star and tree structures are used most often, while data centers use modern topologies such as Spine-Leaf or Clos.

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#Cheat sheet (5 seconds before the interview)

• Bus - a shared cable (outdated).
• Star - the most common option.
• Ring - rare, historical.
• Tree - corporate LANs.
• Mesh - high fault tolerance, DC and Wi-Fi mesh.
• Spine-Leaf / Clos - modern data centers.