3.1. Routing Technologies

💡 First Principle: Routing moves packets between networks. Without routing, networks remain isolated islands—devices communicate locally but can never reach other subnets or the internet. Routers build maps of reachable networks and forward packets based on those maps.

What breaks without routing knowledge? Configure a static route to the wrong next-hop, and traffic black-holes—packets leave but never arrive. Choose OSPF for a two-router network, and you've added complexity without benefit. Ignore administrative distance during route redistribution, and suboptimal paths win because you didn't understand the selection hierarchy.

Think of routing like GPS navigation: static routes are manually programmed turns (simple but inflexible—road closed and you're stuck). Dynamic routing protocols are real-time traffic-aware navigation (automatically adapts to changes).