350-401 Question #521: Real Exam Question with Answer & Explanation

Question

Refer to the exhibit. Router BRDR-1 is configured to receive the 0.0.0.0/0 and 172.17.1.0/24 networks via BGP and advertise them into OSPF area 0. An engineer has noticed that the OSPF domain is receiving only the 172.17.1.0/24 route and default route 0.0.0.0/0 is still missing. Which configuration must an engineer apply to resolve the problem?

Options

• Arouter ospf 1 redistribute bgp 65001 metric 100 route-policy BGP-TO-OSPF end
• Brouter ospf 1 default-information originate end
• Crouter ospf 1 default-metric 100 end
• Drouter ospf 1 default-information originate always end

Explanation

To resolve the issue of a BGP-learned default route not being advertised into OSPF, the OSPF process must be explicitly configured to originate default information.

Common mistakes.

• A. While redistribute bgp is necessary to bring BGP routes into OSPF, it typically does not by itself originate a default route (0.0.0.0/0) into OSPF, requiring an explicit default-information originate command.
• B. The default-information originate command without always will only advertise a default route if the router already has an active default route in its routing table, but always provides a more robust guarantee of propagation in all circumstances.
• C. The default-metric command sets the metric for routes being redistributed into OSPF, but it does not enable the advertisement of the default route itself.

Concept tested. OSPF default route origination

Reference. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/command/ospf-cr-book/ospf-cr-d1.html#wp2457053597

No community discussion yet for this question.