How often do distance-vector protocols typically send updates, and what is the effect on the network?

• A. Only on demand.
• B. Periodically (e.g., every 30 seconds in RIP); regular updates propagate topology changes but add bandwidth.
• C. Every second.
• D. Never.

Answer: (B)

In distance-vector routing, routers share their view of the network with neighboring routers at regular intervals. This periodic exchange keeps all routers informed about reachable destinations and their costs, letting the network gradually converge when changes happen. In practical implementations like RIP, those updates occur on a fixed timer (every 30 seconds). Because updates are sent routinely, topology changes propagate through the network as information is refreshed, so everyone learns about new routes. The trade-off is that this periodic traffic consumes bandwidth on every link and adds processing load, even if nothing has changed. This is why periodic updates are common: they ensure visibility and convergence, but they do add overhead to the network.