Cisco CCNA mock exam questions sample test – Question 345

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. 110
B. 2
C. 3
D. 7

Correct Answer: B

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.

Routing Fundamentals
Configure, verify, and troubleshoot single area and multi-area OSPFv2 for IPv4 (excluding authentication, filtering, manual summarization, redistribution, stub, virtual-link, and SAs)
Home > Support > Technology Support > IP > IP Routing > Technology Information > Technology White Paper > OSPF Design Guide > OSPF Cost