200-301 Question #1625: Real Exam Question with Answer & Explanation

Question

Refer to the exhibit. With a reference bandwidth of 100 Gb on all routers, which path does router Y use to get to network 192.168.1.0/24?

Options

• Arouter C > D > A > F
• Brouter E > F
• Crouter E > B > F
• Drouter C > D > A > B > F

Explanation

Router Y selects the path to network 192.168.1.0/24 based on the lowest cumulative OSPF cost, calculated from the reference bandwidth and interface speeds.

Common mistakes.

• A. Path A is incorrect because its cumulative OSPF cost must be higher than path D, implying its links have lower bandwidths and thus higher individual costs.
• B. Path B is incorrect because its shorter hop count does not guarantee a lower OSPF cost; its links likely have lower bandwidths, leading to a higher total cost.
• C. Path C is incorrect because its cumulative OSPF cost, even with three hops, must be higher than path D due to assumed lower bandwidth links and higher individual costs.

Concept tested. OSPF path selection and cost calculation

Reference. https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/7039-1.html

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