300-510 Question #254: Real Exam Question with Answer & Explanation

Question

Refer to the exhibit. OSPF is an interior routing protocol on the network. R2 is in the backbone area, and R4 is in a totally NSSA area. R5 announces only the 0.0.0.0/0 route to R4 via BGP. R4 is configured with redistribute bgp 736 metric-type 2. After the most recent maintenance window, R2 no longer has the default route via R4. Which action must the network engineer take to correct the reachability problem?

Options

• AConfigure area 2 nssa no-summary under the global router configuration on router R2.
• BConfigure default-information-originate under the OSPF configuration on router R4.
• CConfigure ip route 0.0.0.0 0.0.0.0 null0 under the global router configuration on router R4.
• DConfigure area 2 nssa translate type7 no-suppress-fa under the OSPF configuration on router R2.

Explanation

R4 is part of a totally NSSA area (area 2) and receives a default route 0.0.0.0/0 via BGP. OSPF NSSA uses Type 7 LSAs for routes redistributed into the NSSA, which are then translated into Type 5 LSAs at the ABR (R2 in this case). R2 no longer has the default route because the Type 7 LSA is not being translated into a Type 5 LSA. By default, an ABR translates Type 7 LSAs into Type 5 LSAs, but certain conditions or configurations (e.g., suppress-fa) can prevent this translation. area 2 nssa translate type7 no- suppress-fa ensures that R2 translates the Type 7 LSA (from R4) into a Type 5 LSA. This allows the default route 0.0.0.0/0 to propagate from R4 to R2 and the rest of the OSPF network.

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