CISCO CCNA 200-301 Q29

Examine the following diagram:

While troubleshooting an OSPF routing problem, you need to determine the cost for Router F to reach the 24 network via the best route. What will that cost be?

A. 2
B. 3
C. 7
D. 110

Correct Answers: A

The best route to the network from the perspective of router F will have an OSPF assigned cost of 2. There are three possible loop-free paths to get from router F to the network. The default OSPF costs for a 100 MB link, a T1 link, and a T3 link are 1, 64, and 2, respectively.

The three paths and the calculation of their costs are shown:

Router F to Router E to Router A: 1 + 1 = 2 Router F to Router C to Router A: 2 + 1 = 3
Router F to Router B to Router D to Router C to Router A: 64 + 64 + 64 + 1 = 193

Each OSPF route calculates the cost of its path to a network, and passes that value on to the next router, which will then add to it the cost to reach that neighbor. For example, the routing table of Router E would look like this for the route to

O [110/1] via

Router F would add its own cost to reach Router E to the cost of reaching, resulting in the following output:

O [110/2] via
110 is the administrative distance of OSPF.