When a router receives a routing table update, how does the metric for that path typically change?

When a router receives a routing table update, how does the metric for that path typically change?

• A. Increased by 2
• B. Decreased by 1
• C. Increased by 1
• D. Decreased by 2

Answer: (C)

In distance-vector routing, the cost to reach a destination is calculated by adding the cost to reach the neighbor that sent the update to the cost that the neighbor reports. When a route update arrives, you take the neighbor’s advertised metric and add the cost to reach that neighbor. For most networks, the cost to reach a directly connected neighbor is one hop, so the total metric becomes one more than what the neighbor advertised. That’s why the typical change is an increase by 1. The other options would imply a different hop cost to the neighbor or a decrease of metric, which doesn’t match the standard update rule where the next-hop cost is added to the neighbor’s metric.

In distance-vector routing, the cost to reach a destination is calculated by adding the cost to reach the neighbor that sent the update to the cost that the neighbor reports. When a route update arrives, you take the neighbor’s advertised metric and add the cost to reach that neighbor. For most networks, the cost to reach a directly connected neighbor is one hop, so the total metric becomes one more than what the neighbor advertised. That’s why the typical change is an increase by 1.

The other options would imply a different hop cost to the neighbor or a decrease of metric, which doesn’t match the standard update rule where the next-hop cost is added to the neighbor’s metric.