Refer to the exhibit.

A (Change OSPF reference bandwidth): OSPF calculates path cost based on interface bandwidth using a formula where cost = reference bandwidth / interface bandwidth. The default OSPF reference bandwidth is 100 Mbps, which causes all faster links (1 Gbps and above) to appear with the same minimum cost.

Updating the reference bandwidth (e.g., to 10000 or higher) allows OSPF to assign accurate costs to faster links, enabling proper path selection that reflects real link capacities.

Other options explained:

B: Filtering is not the correct method for path optimization.

C: Changing interface bandwidth values is a workaround but not scalable or recommended compared to updating the reference bandwidth globally.

D: Summarization addresses prefix aggregation, not cost calculation.

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