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300-415 · Question #429
300-415 Question #429: Real Exam Question with Answer & Explanation
The correct answer is C: area 1 nssa default-information-originate. To redistribute OMP routes into OSPF as type 7 LSAs and inject a default route into an NSSA, the engineer must configure Area 1 as NSSA with default-information-originate and redistribute OMP routes into OSPF.
WAN Edge Router Deployment
Question
Refer to the exhibit. CSRV1 must redistribute OMP routes into OSPF Area 1 that must be seen as type 7 LSA by RTR1. CSRV1 must also advertise the default route toward RTR1, which is learned via OMP. Which two configurations must the engineer implement to meet these requirements? (Choose two.)
Options
- Aarea 1 stub no-summary
- Bdefault-information originate always
- Carea 1 nssa default-information-originate
- Dredistribute omp subnet
- Earea 1 nssa no-summary
Explanation
To redistribute OMP routes into OSPF as type 7 LSAs and inject a default route into an NSSA, the engineer must configure Area 1 as NSSA with default-information-originate and redistribute OMP routes into OSPF.
Common mistakes.
- A. 'area 1 stub no-summary' configures Area 1 as a totally stubby area, which blocks all external LSAs and does not support type 7 LSAs that NSSA requires.
- B. 'default-information originate always' injects a type 5 (external) LSA default route into normal OSPF areas, but type 5 LSAs are not flooded into NSSA - only type 7 LSAs are valid inside NSSA.
- E. 'area 1 nssa no-summary' creates a totally NSSA (blocking inter-area summary LSAs) but does not automatically originate a default route toward the NSSA, leaving RTR1 without a default.
Concept tested. OSPF NSSA type 7 LSA and OMP redistribution
Reference. https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/6208-nssa.html
Topics
#OSPF NSSA#Route Redistribution#Default Route Origination#Type 7 LSA
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