In the simplest terms, dynamic routing serves exactly the same purpose as static routing. It associates destination IP prefixes with the next hop IP addresses through which they can be reached, thereby allowing the construction of forwarding table entries for reaching them.
But dynamic routing is different from static routing in that it is based not on static configuration, but on the dynamic interplay of routing protocols across a live IP network, as shown in Figure 11-4.
Figure 11-4. Dynamic routing communication
This dynamic interplay is what makes dynamic routing so much more powerful and resilient in the real world. Routing protocols continually exchange and update routing information between IP routing devices as network conditions change.
Real networks are not predictable or static. Devices fail. Connections fail. Whole networks fail. When these unpredictable events occur, network administrators are held accountable by their organizations. This is why dynamic routing is so important.
Where a simple static route may easily (and unknowingly) point toward an unusable network path, a dynamic route has the power to change through newly learned information, as shown in Figure 11-5.
Figure 11-5. Dynamic routing convergence
This simple concept of dynamically converging around ...