What Are Network Topologies?
Table of Contents
What Topology Means
A network topology describes how devices are connected to each other. Physical topology is the actual cable layout. Logical topology is how data flows through the network, which can differ from the physical arrangement.
Topology affects performance, fault tolerance, scalability, and cost. A mesh provides redundancy but requires many connections. A star is simple and scalable but has a single point of failure at the center. Choosing the right topology depends on what matters most for the deployment.
Bus Topology
All devices share a single cable (the bus). Data travels in both directions along the bus, and every device sees every frame. Only the intended recipient processes the frame; all others ignore it.
Early Ethernet (10BASE2, 10BASE5) used bus topology with coaxial cable. The bus was one collision domain - only one device could transmit at a time. A break anywhere in the cable took down the entire network. Bus topology is obsolete for wired networks but the concept persists in WiFi, where the radio channel functions as a shared bus.
graph TD
subgraph "Star"
S_C["Switch"] --- S1["Device"]
S_C --- S2["Device"]
S_C --- S3["Device"]
S_C --- S4["Device"]
end
subgraph "Mesh"
M1["Node"] --- M2["Node"]
M1 --- M3["Node"]
M2 --- M3
M2 --- M4["Node"]
M3 --- M4
end
Star vs mesh: star has a central switch (single point of failure). Mesh has multiple paths (fault tolerant but complex).
Star Topology
Every device connects to a central switch (or hub). All communication passes through the center. If one device's cable fails, only that device loses connectivity. If the central switch fails, the entire network goes down.
Star is the dominant topology for modern wired LANs. Switches at the center provide dedicated bandwidth per port, eliminating the collision problems of bus topology. The single point of failure is mitigated by using redundant switches (stacking, VSS, or dual-homing).
Ring Topology
Each device connects to exactly two neighbors, forming a closed loop. Data travels around the ring in one direction (or both in a dual-ring). Token Ring and FDDI networks used this topology.
Ring provides deterministic access - a token circulates, and only the device holding the token can transmit. This eliminates collisions but adds latency (waiting for the token). Ring topology is largely obsolete for LANs but appears in WANs (SONET/SDH rings for fiber backbone redundancy).
Mesh Topology
Every device connects to multiple other devices. In a full mesh, every device connects to every other device directly. In a partial mesh, each device connects to several (but not all) others.
Mesh provides the highest fault tolerance - multiple paths mean traffic can route around failed links. The cost is complexity: a full mesh of N devices requires N(N-1)/2 connections. Full mesh is impractical for large networks but common for router interconnects in WANs and data center spine-leaf architectures.
The BLEShark Nano's Shiver mesh system uses partial mesh topology over ESP-NOW. Each node connects to its direct neighbors, and AODV routing handles multi-hop paths across the mesh. Up to 16 nodes can form a self-healing mesh where traffic routes around failed links automatically.
Hybrid Topologies
Real-world networks combine topologies. A campus network might use star topology within each floor (switches with device connections), mesh topology between building switches (redundant uplinks), and a ring or partial mesh in the WAN backbone.
The star-mesh hybrid is the most common enterprise design: star at the access layer (devices to access switches), partial mesh at the distribution/core layer (redundant paths between aggregation switches and core routers).
Wireless Topologies
WiFi operates in two topologies: infrastructure mode (star - all clients connect through an AP) and ad-hoc mode (mesh - clients communicate directly). Infrastructure mode dominates because the AP provides coordination, authentication, and bridging to the wired network.
WiFi mesh networking (802.11s) extends coverage by chaining APs wirelessly. Each mesh AP connects to one or more neighbors, forming a wireless mesh backbone. Consumer mesh systems (Google Nest WiFi, Eero, etc.) use this approach to cover large homes without running Ethernet to every AP.