Network topology
Also known as: network topology architecture
Network topology is the arrangement of devices and the links between them in a network. Physical topology describes how the cabling is actually run, while logical topology describes the path data takes through the network regardless of the wiring.
Topology answers a structural question: what connects to what. The distinction between physical and logical topology matters because the two frequently differ. A modern Ethernet LAN is physically a star — every device cabled back to a central switch — while the logical topology, the path frames actually take, is determined by switching and routing decisions.
The classic topology types are basic vocabulary. A bus topology places all devices on one shared cable, so a single break disrupts everything; a ring passes traffic device to device around a loop; a star wires every node to a central device, which localizes failures but makes it a single point of failure. An extended star chains stars together hierarchically, and a mesh connects devices to one another directly — a full mesh links every node to every other, maximizing redundancy at a cost that grows quickly, while a partial mesh adds redundant links only where they matter. Most real networks are hybrids.
Enterprise design uses a layered vocabulary on top of these shapes. The three-tier architecture separates an access layer where end devices connect, a distribution layer that aggregates access switches and enforces policy, and a core layer that moves traffic between distribution blocks at high speed. A two-tier or collapsed core design merges distribution and core, common in smaller campuses. Data centers increasingly use a spine-leaf architecture in which every leaf switch connects to every spine switch, giving predictable equal-length paths for east-west traffic. Small office and home office networks collapse everything into a single device, and WAN topologies — hub-and-spoke, full mesh, point-to-point — describe how sites connect across a service provider.
Topology choices carry direct operational consequences: they determine redundancy, failure domains, how far broadcast traffic spreads, and how easily the network can grow. Redundant links also create switching loops, which is why Spanning Tree Protocol blocks redundant paths logically while leaving them physically in place. The CCNA exam tests network topology architectures explicitly, expecting you to describe two-tier, three-tier, spine-leaf, WAN, small office, and on-premises versus cloud designs.
Key takeaways
- Physical topology describes the actual cabling layout; logical topology describes the path data takes.
- Bus, ring, star, extended star, mesh, and hybrid are the classic topology types.
- Modern Ethernet LANs are physically star or extended star, built around switches.
- Enterprise campus designs use three-tier (access, distribution, core) or collapsed two-tier architectures, while data centers favor spine-leaf.
- Topology determines redundancy, failure domains, and scalability, and redundant links require Spanning Tree Protocol to prevent switching loops.