2.2. Network Topology Architectures

💡 First Principle: Network topology choices are always trade-offs between cost, performance, and resilience. A two-tier design is simpler and cheaper; a three-tier design scales better; spine-leaf optimizes for east-west traffic. The exam tests whether you can match a scenario to the appropriate topology.

Think about how cities design road systems. A small town needs one main street connecting neighborhoods—that's two-tier. A metropolis needs highways (core), major roads (distribution), and local streets (access)—that's three-tier. A warehouse district where trucks constantly move between buildings needs a grid where every intersection connects to every other—that's spine-leaf.

The key insight: there's no "best" topology. The right choice depends on traffic patterns, scale, budget, and redundancy requirements. The exam will give you a scenario and expect you to identify which topology fits.

What happens when you choose wrong: An undersized design creates bottlenecks during growth. An oversized design wastes money on infrastructure you don't need. A topology optimized for north-south traffic will choke in an environment with heavy east-west traffic.