OSPF NSSA Route Summarization on ABR
Short answer
A Route summarization can indeed be configured on an ABR in an NSSA to aggregate Type 7 LSAs translated into Type 5 LSAs, thereby reducing LSA propagation in non-special areas.
Question
Key Takeaways
The key insight is that ABRs not only translate Type 7 LSAs to Type 5 but can also summarize them to minimize LSA flooding across the OSPF domain.
This page explains how OSPF NSSA route summarization works on an ABR to reduce Type 5 LSA count after translating Type 7 LSAs, confirming the statement is True.
Common mistake: A common mistake is assuming that Type 7 LSAs cannot be summarized or that summarization must happen within the NSSA itself rather than at the ABR during translation.
Expert Analysis
NSSA LSA Translation and Summarization
In OSPF, a Not-So-Stubby Area (NSSA) allows external routes to be imported as Type 7 LSAs. These Type 7 LSAs are confined to the NSSA. When they reach an Autonomous Boundary Router (ABR), the ABR translates them into Type 5 LSAs so they can be flooded into other areas, including the backbone area (Area 0).
The question states that route summarization can be configured on an ABR in the NSSA to summarize the routes corresponding to the Type 5 LSAs translated from Type 7 LSAs. This is a standard capability. The ABR performs two functions: it translates Type 7 to Type 5, and it can also aggregate (summarize) these routes before flooding the resulting Type 5 LSAs into other areas. This reduces the number of LSAs in non-special areas.
Therefore, the statement is true. Configuring route summarization on the ABR for NSSA external routes (Type 7 translated to Type 5) helps reduce LSA count and routing table size in other areas.
Exam Strategy
When answering OSPF questions about LSA types and areas, always identify the router role (ABR, ASBR) and the area type (stub, NSSA). For NSSA, remember that Type 7 LSAs are translated to Type 5 by the ABR, and summarization can be applied to these translated routes to optimize network performance.
Frequently Asked Questions
What happens if an ABR does not translate Type 7 LSAs?
Can multiple ABRs summarize NSSA routes?
Community Votes
100% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 1 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 1
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HCIP Resolutor 👍 1 Answered BCuando estas LSAs Tipo 7 llegan al ABR de la NSSA, el ABR las traduce a LSAs Tipo 5 para inundarlas hacia el Backbone (Area 0) y el resto del dominio.
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