Which statement correctly contrasts RIP with modern IGPs?

Which statement correctly contrasts RIP with modern IGPs?

• A. Modern IGPs require manual route summarization
• B. RIP uses hop count metric limited to 15; updates every 30 seconds; slower convergence
• C. Modern IGPs use only hop count and slower convergence
• D. RIP uses link-state routing; modern IGPs use distance-vector

Answer: (B)

RIP uses a simple distance-vector approach with a basic hop-count metric, and it was designed for small networks. The statement that correctly contrasts RIP with modern IGPs notes three key ideas: the hop-count metric is limited to 15 hops, updates happen every 30 seconds, and convergence is slow. The 15-hop maximum means networks beyond that are treated as unreachable, which limits scalability. The fixed 30-second update interval slows the propagation of topology changes, so routers can take longer to learn new paths or to remove dead ones, leading to longer convergence times. Modern IGPs, by contrast, use more expressive metrics (such as cost based on bandwidth) and faster mechanisms for sharing topology changes—often via link-state flooding or rapid distance-vector with triggered updates—so they converge much faster and scale better. Why the other options don’t fit: modern IGPs are not required to use manual route summarization, and in practice they often use automatic or flexible summarization. Modern IGPs are not limited to using only hop count with slower convergence, since they employ richer metrics and faster convergence methods. And RIP is not link-state; modern IGPs include link-state protocols like OSPF/IS-IS (and others) rather than all being distance-vector.

RIP uses a simple distance-vector approach with a basic hop-count metric, and it was designed for small networks. The statement that correctly contrasts RIP with modern IGPs notes three key ideas: the hop-count metric is limited to 15 hops, updates happen every 30 seconds, and convergence is slow. The 15-hop maximum means networks beyond that are treated as unreachable, which limits scalability. The fixed 30-second update interval slows the propagation of topology changes, so routers can take longer to learn new paths or to remove dead ones, leading to longer convergence times. Modern IGPs, by contrast, use more expressive metrics (such as cost based on bandwidth) and faster mechanisms for sharing topology changes—often via link-state flooding or rapid distance-vector with triggered updates—so they converge much faster and scale better.

Why the other options don’t fit: modern IGPs are not required to use manual route summarization, and in practice they often use automatic or flexible summarization. Modern IGPs are not limited to using only hop count with slower convergence, since they employ richer metrics and faster convergence methods. And RIP is not link-state; modern IGPs include link-state protocols like OSPF/IS-IS (and others) rather than all being distance-vector.