4.3. Static Routing (IPv4 and IPv6)

💡 First Principle: Static routes are manually configured paths that don't change unless an administrator modifies them. They're simple, secure (no routing protocol to attack), and use minimal resources—but they don't adapt to topology changes. Use static routes for simple topologies, default routes, and backup paths.

Static routing is the "training wheels" of routing—essential to understand, often used in production, but not suitable for complex or changing networks. When you have only one path to a destination (like a branch office with a single WAN link), why run a routing protocol? A static route is simpler and more predictable.

When to use static routes:

• Stub networks: A branch with only one way out—there's nothing to calculate
• Default routes: "Send everything else to the ISP"—the most common static route
• Backup paths: Floating static routes that activate only when the primary fails
• Security: No routing protocol means no routing protocol attacks

The trade-off: Static routes don't know when links fail. If the next-hop becomes unreachable, the static route just sits there pointing to a black hole (unless you use tracking or floating statics). Dynamic protocols adapt; static routes don't.