Network Topology
Physical and Logical Network Layout
The arrangement of devices and connections in a network — both how cables are physically laid (physical topology) and how data logically flows (logical topology). Topology choices determine redundancy, fault tolerance, and ease of management.
Network topology is the blueprint of a network. Every network has a physical topology (cable runs, device placement) and a logical topology (how data moves). Most home and office networks use star topology: all devices connect to a central switch, which forwards traffic between them. The switch is the single point through which all communications pass — simple to manage, easy to expand, but a single point of failure if the switch fails. Enterprise networks extend this to hierarchical (tree) topologies with multiple switch layers for scale.
Topology types
| Topology | Structure | Fault tolerance | Typical use |
|---|---|---|---|
| Star | All devices connect to central switch | One device failure isolated | Home, office LAN |
| Bus | All devices share one cable | Poor — any break splits network | Legacy coaxial Ethernet, logical Wi-Fi |
| Ring | Devices form a loop | Moderate — dual ring adds redundancy | SONET/SDH WAN, legacy Token Ring |
| Mesh (full) | Every node connects to every other | Very high — many redundant paths | ISP core, military networks |
| Mesh (partial) | Some redundant connections | High — multiple paths exist | Enterprise WAN, mesh Wi-Fi backhaul |
| Tree (hierarchical) | Star-of-stars in layers | Moderate — core failure is critical | Enterprise campus networks |
Topology and redundancy
Star topology has a single point of failure at the central switch — if the switch fails, all connected devices lose connectivity. Enterprise networks address this with dual-homed connections: servers and critical devices connect to two different switches using link aggregation (LACP) or spanning tree. Data centres use spine-leaf topology — a modern variant of partial mesh where every leaf switch connects to every spine switch, providing predictable latency and no oversubscription at the core. ISP backbones use full or near-full mesh topologies between routers to ensure packets always have an alternative path.
Frequently Asked Questions
What is the most common network topology used today?
Star topology dominates modern LANs — every device connects to a central switch. Larger environments use hierarchical (tree) topology: access switches → distribution switches → core switch. Physical ring is rare today but persists logically in SONET/SDH WAN resilience and some ring protocols.
What is the difference between physical and logical topology?
Physical topology is how cables are actually run. Logical topology is how data flows, which may differ. Token Ring was physically a star (cables to a central hub) but logically a ring (data passed sequentially). Wi-Fi is logically a bus (shared medium) with no physical cables between devices.
What topology does mesh Wi-Fi use?
Partial mesh between access points for backhaul (redundant paths, dynamic routing), with star topology from each node to client devices. Full mesh (every node to every node) is rare; partial mesh provides good resilience at reasonable cost.