Which one of these statements is true of OSPF type 5 LSAs?

Question

Options

• AThey are used to summarize area routes to other areas.
• BThey are used in not-so-stubby areas to propagate external routes.
• CThey are used to notify areas of the ASBR.
• DThey are flooded to all areas except stub areas (external route).

• A
  2% (1)
• B
  4% (2)
• C
  6% (3)
• D
  88% (43)

Explanation

OSPF Type 5 LSAs are AS External LSAs generated by ASBRs (Autonomous System Boundary Routers) to advertise routes learned from outside the OSPF domain (e.g., redistributed static or BGP routes). They are flooded throughout the entire OSPF autonomous system EXCEPT into stub areas and NSSAs - stub areas block Type 5 LSAs entirely. Option A is wrong: summarizing area routes to other areas is done by Type 3 Summary LSAs. Option B is wrong: NSSAs use Type 7 LSAs for external routes, not Type 5. Option C is wrong: notifying areas about an ASBR's existence is the job of Type 4 ASBR Summary LSAs. Option D is the correct characterization - Type 5 LSAs are flooded everywhere except stub areas.

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