2.6. Network Topologies and Architectures

💡 First Principle: Network topology—how devices physically and logically connect—determines fault tolerance, scalability, and performance. Physical topology is how cables actually run; logical topology is how data flows. They don't always match, and understanding both matters for design and troubleshooting.

What breaks without topology understanding? Build a star topology with a cheap hub at the center—that hub becomes a single point of failure. Design a three-tier hierarchy for a 20-device office—you've overcomplicated and overspent. Use hub-and-spoke for east-west traffic patterns—every packet takes an inefficient path through the central hub.

Think of topology like city planning: a star is downtown with suburbs radiating out (simple but congested at center), a mesh is a grid of interconnected streets (resilient but expensive), and spine-leaf is a highway system where any on-ramp connects to any exit in exactly two hops.