3.1.1. Static vs. Dynamic Routing
Static Routing: Manually configured by administrators. You specify: "To reach network X, send packets to next-hop Y."
| Pros | Cons |
|---|---|
| Simple to configure | Doesn't adapt to failures |
| Predictable behavior | Doesn't scale to large networks |
| No routing protocol overhead | Manual updates required |
| Secure (no routing updates to spoof) | Administrator must know topology |
Dynamic Routing: Routers automatically discover routes by exchanging information with neighbors.
| Protocol | Type | Algorithm | Use Case |
|---|---|---|---|
| BGP | Path vector | Best path selection based on policies | Internet routing, between organizations |
| OSPF | Link state | Dijkstra (shortest path first) | Enterprise internal routing |
| EIGRP | Advanced distance vector | DUAL (Diffusing Update Algorithm) | Cisco environments |
BGP (Border Gateway Protocol): The protocol that makes the internet work. Routes between autonomous systems (organizations). Makes decisions based on policies (business relationships) not just metrics.
OSPF (Open Shortest Path First): Every router builds a complete topology map. All routers have the same view and independently calculate shortest paths. Changes propagate quickly because routers share link-state information, not just distances.
EIGRP (Enhanced Interior Gateway Routing Protocol): Cisco-developed protocol combining benefits of distance-vector (simplicity) and link-state (fast convergence). Uses composite metric based on bandwidth and delay.
