352-001 Question #357: Real Exam Question with Answer & Explanation

The correct answer is D: on the routing process of all ABR routers. OSPF summarization can only be configured in the OSPF routing process, not on individual interfaces, and only ABRs and ASBRs have the role to summarize inter-area and external routes respectively.

Question

The network architect wants to reduce the OSPF database in the network by using summarization techniques. In which two places in the network can summarization be applied to maximum effect? (Choose two.)

Options

Aon the OSPF links of all ABR routers
Bon the OSPF links of all ASBR routers
Con the OSPF links of all backbone routers
Don the routing process of all ABR routers
Eon the routing process of all ASBR routers
Fon the routing process of all backbone routers

Explanation

OSPF summarization can only be configured in the OSPF routing process, not on individual interfaces, and only ABRs and ASBRs have the role to summarize inter-area and external routes respectively.

Common mistakes.

A. Summarization in OSPF is not configured on a per-interface or per-link basis; the ip ospf interface commands control authentication, timers, and costs, not prefix aggregation.
B. Summarization cannot be applied to OSPF links on ASBRs; the summary-address command must be applied in the OSPF routing process, not on individual interfaces.
C. Backbone routers (internal area 0 routers that are not ABRs or ASBRs) do not have summarization capability because they do not sit on inter-area or redistribution boundaries.
F. Internal backbone routers that are not ABRs or ASBRs have no OSPF summarization commands available in their routing process; only ABRs and ASBRs perform summarization.

Concept tested. OSPF summarization placement at ABR and ASBR routing processes

Reference. https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/5110-12.html

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