Network Topology
Bus, star, ring, mesh, hybrid — how nodes are wired, logically and physically.
Level: beginner
What is it?
Network topology describes how devices and links are arranged physically and how traffic flows logically. Common physical or logical patterns include star, bus, ring, mesh, tree, and hybrid layouts.
Why does it matter?
Topology influences failure domains, redundancy, cost, broadcast behavior, and how easy a network is to expand or troubleshoot. The physical cable layout and logical forwarding topology may differ.
Mental model
Draw devices as nodes and links as edges, then ask whether a failed node or edge disconnects the graph and whether loops exist. The diagram should describe the relevant layer and not mix physical wiring with logical paths.
How it works
- A star connects endpoints to a central switch or hub; the central device is a shared dependency.
- A full mesh offers many alternate paths but grows in link count rapidly as the number of nodes increases.
- A ring provides a structured path but needs a protocol or design for handling link failures and loop behavior.
- Tree and hierarchical designs scale through access, distribution, and core roles but need careful redundancy planning.
- Logical topologies depend on protocol behavior; Ethernet switched paths and overlay networks may not match cable diagrams.
Steps
- List the nodes and links at the layer being designed.
- Mark critical endpoints and links whose failure would disconnect sites or overload a remaining path.
- Identify loops and whether the forwarding protocol blocks or manages them.
- Test a failure scenario and verify convergence, capacity, and monitoring.
Real-world usage
- Planning campus, data-center, and office networks.
- Troubleshooting a single point of failure or an unexpected forwarding loop.
Common mistakes
- Calling a topology fault-tolerant without testing alternate paths and failover.
- Confusing physical star wiring with a single logical broadcast domain.
- Drawing redundant links without accounting for loop-prevention or routing protocols.
Interview questions
What is the major failure dependency of a star topology?
The central switch or hub is a dependency for communication across its connected spokes, unless the design includes additional redundancy.
Why can a mesh become expensive?
The number of potential point-to-point links grows quickly; a full mesh of n nodes has n(n−1)/2 links.