Part 4. Dynamic routing and first hop redundancy protocols

After focusing on Layer 2 concepts in part 3, part 4 is a return to Layer 3. In chapter 9, we covered static routes, which involve manually configuring routes on each router as necessary. That manual approach is simply not feasible in larger networks, and chapter 17 introduces a more scalable approach: dynamic routing. Dynamic routing protocols enable routers to communicate with each other and share routing information automatically, without the need to manually configure each router’s routing table. Then, chapter 18 focuses on Open Shortest Path First (OSPF), one of the most commonly used dynamic routing protocols, and a major topic on the CCNA exam.

Chapter 19 moves away from the topic of dynamic routing to a different kind of protocol available on Cisco routers: first hop redundancy protocols (FHRPs). FHRPs enable multiple routers to team up to provide a resilient default gateway for hosts in a LAN; if a hardware failure or a similar issue affects one router, the other router is ready to take over and ensure that hosts in the LAN maintain continuous connectivity. FHRPs are a key tool in modern networks, which are expected to be reliably available on a 24/7 basis.