Understanding OSPF Route Metrics and Types

B

The command "show ospf route" is used to display the OSPF routes currently in the routing table. If you see routes with a metric type of EXT2, it means that these routes have been redistributed into OSPF and are using a Type 2 metric.

To understand this in more detail, let's first review some basic OSPF concepts:

• OSPF (Open Shortest Path First) is a routing protocol used in IP networks.
• OSPF operates by exchanging information between routers about the networks they are connected to, and then calculating the shortest path to reach each network based on that information.
• OSPF assigns a metric to each route, which is used to determine the best path to a network. The metric is based on the cost of the path, which is calculated using a formula that takes into account the bandwidth of the link and any other relevant factors.
• OSPF defines several types of metrics, including Type 1 and Type 2 metrics.

Now, let's focus on the metric types:

• Type 1 metrics are used for intra-area routes, which are routes within a single OSPF area. Type 1 metrics are calculated based on the cost of the path within the area.
• Type 2 metrics are used for inter-area routes, which are routes between different OSPF areas. Type 2 metrics are calculated based on the cost of the path from the originating router to the destination area, plus the cost of the path within the destination area.

So, when you see routes with a metric type of EXT2, it means that these routes have been redistributed into OSPF and are using a Type 2 metric. This indicates that the routes are inter-area routes, and the metric is based on the cost of the path from the originating router to the destination area, plus the cost of the path within the destination area.

Therefore, the correct answer to this question is B: These routes have been redistributed into OSPF and are using a Type 2 metric.