In RIPv2, which metric is used to select the best path to a remote network?

Introduction / Context:
Different routing protocols use different metrics to evaluate and choose the best path to a destination network. Understanding which metric a protocol uses is fundamental for predicting routing behaviour and for tuning the network. RIPv2 is a classic distance vector protocol that uses a simple metric, which is one of the reasons it is easy to configure but limited in large topologies.

Given Data / Assumptions:

• RIPv2 is running in a network of Cisco routers.
• The protocol exchanges routing updates using UDP and sends the full routing table periodically.
• You want to know what single numeric value RIPv2 compares when selecting the best path.
• Other protocols such as EIGRP and OSPF use more complex metrics, but this question is specifically about RIPv2.

Concept / Approach:
RIPv2 uses hop count as its metric. Each router that a packet crosses to reach a destination increments the hop count by one. The path with the fewest hops is considered the best. If the hop count exceeds a maximum value, the route is considered unreachable. For RIP, this maximum is 15 hops, so any route with a metric of 16 is treated as unreachable. RIPv2 does not consider bandwidth, delay, load, or reliability in its metric calculation.

Step-by-Step Solution:
Step 1: Recall that RIPv2 is a distance vector protocol that sends full routing table updates every 30 seconds by default.Step 2: Each route in a RIP update includes a hop count metric, which is the number of routers between the advertising router and the destination network.Step 3: When a router receives multiple routes to the same network, it compares the hop counts and installs the route with the lowest value into its routing table.Step 4: If all advertised hop counts for a particular network are 16 or higher, the destination is considered unreachable and no route is installed.Step 5: Because hop count is the only metric, two different paths with the same number of hops are considered equal, even if their bandwidth or delay characteristics differ.

Verification / Alternative check:
You can verify the use of hop count by enabling debug ip rip and observing the metrics in updates, or by using show ip route to see the RIP routes with their hop counts. These outputs clearly show that RIPv2 bases its path selection solely on the hop count value.

Why Other Options Are Wrong:
Option B, MTU, is not used by RIP as a path selection metric.Option C and Option D relate more to protocols that consider delay and load, but RIPv2 does not incorporate these values.Option E describes a composite metric closer to what EIGRP uses, not RIP.

Common Pitfalls:
A common misconception is that all modern routing protocols consider bandwidth or delay. RIPv2 remains simple and uses hop count, which can lead to suboptimal routing if a path with more bandwidth has more hops than a slower path. This simplicity is one reason RIPv2 is recommended only for small or simple networks.

Final Answer:
RIPv2 uses Hop count as its metric to choose the best path to a remote network.