200-301 Question #154: Real Exam Question with Answer & Explanation

Question

Refer to the exhibit. The default-information originate command is configured under the R1 OSPF configuration. After testing, workstations on VLAN 20 at Site B cannot reach a DNS server on the Internet. Which action corrects the configuration issue?

Options

• AAdd the default-information originate command on R2.
• BAdd the always keyword to the default-information originate command on R1.
• CConfigure the ip route 0.0.0.0 0.0.0.0 10.10.10.18 command on R1.
• DConfigure the ip route 0.0.0.0 0.0.0.0 10.10.10.2 command on R2.

Explanation

For default-information originate to propagate a default route into OSPF, the originating router (R1) must have a default route (0.0.0.0/0) in its own routing table.

Common mistakes.

• A. R2 is an internal router in the OSPF domain and does not directly connect to the Internet; adding default-information originate on R2 would not resolve the issue of R1 not having a default route to redistribute.
• B. Adding the always keyword would force R1 to advertise a default route even if it doesn't have one, which would result in blackholing traffic because R1 wouldn't know how to reach the Internet itself.
• D. Configuring a default route on R2 pointing to 10.10.10.2 (R1) is unnecessary for R2 to learn a default route from R1 via OSPF, and it doesn't solve R1's inability to originate the default route.

Concept tested. OSPF default route origination prerequisites

Reference. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/15-mt/iro-ospf-15-mt-book/iro-cfg-ospfv3.html#GUID-AE971165-42CE-4015-81E9-02688A6E2436

No community discussion yet for this question.