Common Topologies
| Topology | How it works | Where you see it today |
|---|---|---|
| Bus | All devices share one linear medium; collisions limited capacity | Legacy 10BASE2 coax Ethernet; historically common before switches |
| Ring | Each node connects to exactly two neighbours forming a loop | Token Ring (largely obsolete); some SONET/SDH metro rings; industrial PROFINET |
| Star | Every device connects to a central switch or access point | Modern switched Ethernet; every home router and office switch |
| Mesh | Nodes connect to multiple other nodes; multiple paths exist | Carrier backbone networks; Wi-Fi mesh systems; SD-WAN overlays |
| Tree | Hierarchical star-of-stars with core, distribution, and access layers | Enterprise campus networks; data centre fabric |
| Hybrid | Combines two or more topologies | Virtually every real-world network |
Bus Topology
Bus topology was the foundation of early Ethernet. All devices attached to a single shared coaxial cable. Any device wishing to transmit had to check whether the medium was idle first (CSMA/CD). Collisions were common as the segment grew, and a break anywhere in the cable took the entire segment down. 10BASE2 (thin coax) and 10BASE5 (thick coax) used this model. Bus topology is essentially obsolete in modern networking, replaced entirely by switched star designs, but understanding it clarifies why switches were such a significant improvement.
Ring Topology
In a ring, each node has exactly two connections: one to the previous node and one to the next, forming a closed loop. Token Ring networks passed a token around the ring; only the device holding the token could transmit, eliminating collisions but limiting throughput. Ring topologies have mostly disappeared from LAN environments. They survive in certain industrial protocols and in transport networks where SONET/SDH rings use the loop structure to enable rapid failover: if one segment fails, traffic reroutes the other way around the ring within milliseconds.
Star Topology
Modern switched Ethernet is a star topology. Every device has a dedicated point-to-point link to a central switch. The switch learns which MAC addresses are on which ports and forwards frames only to the correct destination port rather than broadcasting to all ports. This eliminates collisions, provides dedicated bandwidth per port, and makes fault isolation straightforward: if one device or cable fails, no other device is affected. Star is the default topology for any new wired installation.
Mesh Topology
A full mesh connects every node to every other node directly, providing maximum redundancy and minimum hop count between any pair. Full mesh is impractical at scale because the number of links grows as n(n-1)/2. A partial mesh connects only some nodes to multiple peers, providing redundancy on the most critical paths while reducing cabling or circuit costs. Carrier backbone networks use partial mesh between major PoPs (Points of Presence). Consumer Wi-Fi mesh systems use a partial mesh model where nodes connect to the main router either wirelessly or via wired backhaul, and some systems allow node-to-node wireless links for extended coverage.
Tree (Hierarchical) Topology
Enterprise and campus networks are almost always tree topologies. The hierarchy has three layers: core switches (fast, high-capacity, minimal policy), distribution switches (aggregation, inter-VLAN routing, policy enforcement), and access switches (end-device connections). Each layer fans out to the next. Uplinks from access to distribution must carry aggregate traffic from all access ports; uplinks from distribution to core must carry aggregate traffic from multiple distribution switches. Sizing uplinks correctly is a fundamental design task in tree networks.
Logical vs Physical Topology
The physical topology is what you see in the rack and cable plant. The logical topology is how traffic actually flows. These can differ significantly. A physical star with redundant uplinks may run Spanning Tree Protocol (STP), which logically blocks some ports to prevent loops — turning redundant physical paths into an active/standby logical tree. VLANs partition one physical switch into multiple logical broadcast domains. A VPN tunnel creates a logical point-to-point link across an arbitrarily complex physical internet path. Understanding the logical topology matters as much as the physical layout when troubleshooting.
Spanning Tree Protocol and Redundant Links
Physical star and tree topologies with redundant uplinks create loops at Layer 2. Ethernet frames have no TTL, so a loop would circulate frames indefinitely, consuming all bandwidth within seconds. STP (IEEE 802.1D) and its faster successors RSTP (802.1w) and MSTP (802.1s) prevent this by electing a root bridge and placing redundant ports into a blocking state. Blocked ports carry no traffic under normal conditions but transition to forwarding if the active path fails. Modern data centres often replace STP with MLAG or routed fabric designs that allow all links to be active simultaneously.
Topology Effects on Fault Tolerance and Latency
Topology choices directly determine how failures propagate and how many hops traffic must traverse. A single switch failure in a star takes down all devices connected to it. A partial mesh provides alternate paths so traffic reroutes around a failure. Each additional hop adds forwarding latency — typically sub-millisecond on gigabit equipment, but meaningful when many hops stack up. In Wi-Fi mesh systems, a wireless hop adds several milliseconds of latency and consumes airtime; devices two wireless hops from the router see noticeably higher latency than devices one hop away.
Home Network Topology
Most home networks are a star or hybrid topology. Wired devices connect to a switch or the router's built-in switch ports. Wi-Fi devices connect to an access point. A wired star is the most predictable design: each Ethernet run has dedicated full-duplex capacity back to the switch. Adding mesh nodes creates a hybrid topology where clients connect to the nearest node and nodes connect back to the router via wired or wireless backhaul. Wireless backhaul shares airtime and is sensitive to placement; wired backhaul preserves the star's performance characteristics.
Frequently Asked Questions
What is a network topology?
A network topology is the way devices and links are arranged, either physically in cabling and hardware or logically in traffic flow. The two can differ when protocols like STP, VLANs, or VPNs alter how traffic actually moves.
What topology do home networks usually use?
Most home networks are a star or hybrid topology, with devices connecting to a central router, switch, or mesh system.
Is mesh always better than star?
No. Mesh improves coverage and redundancy in some designs, but wired star networks are simpler, faster, and more predictable when cabling is practical.