Which three statements accurately describe OSPF route summarization? (Choose three.)

Question

Options

• AOSPF routes can be summarized at any OSPF router in the network using area range or summary
• BOSPF internal routes can be summarized only at the ABRs.
• COSPF type 5 external routes can be summarized only at the ASBRs.
• DRoute summarization can lead to a more stable network.
• EOSPF internal routes are automatically summarized via type 3 summary LSAs.
• FA flat addressing scheme is required in order to summarize OSPF routes.

• B
  95% (19)
• F
  5% (1)

Explanation

OSPF has strict rules about where summarization can occur, unlike distance-vector protocols. Internal (intra-area and inter-area) routes can only be summarized at Area Border Routers (ABRs) using the 'area X range' command - ABRs are the boundary between areas and are the only routers authorized to aggregate Type 3 Summary LSAs sent into adjacent areas (B is correct). External routes redistributed into OSPF (Type 5 LSAs) can only be summarized at the Autonomous System Boundary Router (ASBR) using the 'summary-address' command - the ASBR is where external prefixes enter the OSPF domain (C is correct). Route summarization leads to a more stable network (D is correct) because a topology change within a summarized block does not trigger LSA flooding throughout the entire OSPF domain - only the summarizing router recalculates; the summary itself remains unchanged. Option A is wrong because summarization cannot be done at arbitrary routers. Option E is wrong because OSPF does NOT perform automatic summarization - this is a distance-vector concept; OSPF is link-state and requires manual configuration. Option F is wrong because summarization requires a hierarchical (contiguous) addressing scheme, not a flat one.

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