Refer to the exhibit. After a recent network implementation project, customer A is performing stress testing to verify network redundancy at the branch office connected to R4. When the link from R2…

Question

Exhibit

Options

• AConfigure two OSPF processes on R2 and R3 and redistribute traffic between them.
• BRedistribute routes from BGP to OSPF as type E1.
• CUse multiarea adjacency to extend Area 10 to the link between R2 and R3.
• DCreate a virtual channel from R3 to R4.

• A
  5% (1)
• B
  74% (14)
• C
  16% (3)
• D
  5% (1)

Explanation

This scenario involves OSPF external route redistribution from BGP, and the behavior difference between OSPF external type E1 and E2 routes. When BGP routes are redistributed into OSPF as the default type E2, the external metric is fixed and does not accumulate internal OSPF costs. So even when the SLA tracking object raises R2's link cost to 100, the E2 route via R2 still has the same external metric as the E2 route via R3 - OSPF cannot differentiate them based on internal path cost, so the original path via R2 may persist. Redistributing as type E1 changes this behavior: the total cost of an E1 route equals the external metric plus the cumulative internal OSPF cost to reach the ASBR. When R2's internal link cost increases to 100, the E1 route through R2 becomes more expensive than the E1 route through R3, causing OSPF to correctly prefer R3. Option A (two OSPF processes with redistribution) adds unnecessary complexity. Option C (multiarea adjacency) does not solve the metric comparison problem. Option D ('virtual channel') is not a standard OSPF mechanism.

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