Refer to the exhibit. A customer runs OSPF with Area 5 between its aggregation router and an internal router. When a network change occurs in the backbone, Area 5 starts having connectivity issues due

OSPF requires all routers within an area to agree on stub area configuration; enabling stub only at the ABR while Router B does not support it would prevent OSPF adjacency formation in Area 5.

Increasing link bandwidth addresses throughput capacity and has no effect on the volume of LSAs entering Area 5 or the frequency of SPF recalculations.

LSA throttling slows the rate at which LSAs are regenerated and flooded but does not prevent external or specific LSAs from entering Area 5 and still triggering SPF runs.

By configuring the ABR to filter outbound Type 3 LSAs - allowing only aggregate summary routes and blocking more-specific and external LSAs from the backbone - Area 5 receives far fewer topology changes, which directly reduces the number of SPF calculations. This approach mimics stub area behavior at the ABR level without requiring any configuration change on Router B. The result is a more resilient Area 5 that is shielded from backbone churn while respecting the hardware limitation.

A virtual link logically extends Area 0 connectivity but does not filter LSAs and would not reduce the number of topology changes propagated into Area 5.