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350-401 · Question #218

Refer to the exhibit. Which command when applied to the Atlanta router reduces type 3 LSA flooding into the backbone area and summarizes the inter-area routes on the Dallas router?

The correct answer is C. Atlanta(config-route)#area 1 range 192.168.0.0 255.255.252.0. To reduce Type 3 LSA flooding into the OSPF backbone area and summarize inter-area routes from Area 1, the area 1 range command with an appropriate summary address must be applied on the Atlanta ABR.

Submitted by chen.hong· Mar 6, 2026Infrastructure

Question

Refer to the exhibit. Which command when applied to the Atlanta router reduces type 3 LSA flooding into the backbone area and summarizes the inter-area routes on the Dallas router?

Exhibits

350-401 question #218 exhibit 1
350-401 question #218 exhibit 2

Options

  • AAtlanta(config-route)#area 0 range 192.168.0.0 255.255.248.0
  • BAtlanta(config-route)#area 0 range 192.168.0.0 255.255.252.0
  • CAtlanta(config-route)#area 1 range 192.168.0.0 255.255.252.0
  • DAtlanta(config-route)#area 1 range 192.168.0.0 255.255.248.0

How the community answered

(27 responses)
  • A
    4% (1)
  • B
    4% (1)
  • C
    81% (22)
  • D
    11% (3)

Why each option

To reduce Type 3 LSA flooding into the OSPF backbone area and summarize inter-area routes from Area 1, the `area 1 range` command with an appropriate summary address must be applied on the Atlanta ABR.

AAtlanta(config-route)#area 0 range 192.168.0.0 255.255.248.0

The `area 0 range` command is incorrect because summarization for routes originating in a non-backbone area (like Area 1) is configured using the non-backbone area ID (e.g., `area 1`) on the ABR.

BAtlanta(config-route)#area 0 range 192.168.0.0 255.255.252.0

The `area 0 range` command is incorrect for summarizing routes originating from Area 1 into Area 0; the command should specify `area 1` as the source area for summarization.

CAtlanta(config-route)#area 1 range 192.168.0.0 255.255.252.0Correct

The `area <area-id> range <ip-address> <mask>` command is used on an ABR (Area Border Router) to summarize Type 3 LSAs originating from the specified `area-id` (Area 1 in this case) before they are advertised into the backbone (Area 0), thus reducing LSA flooding. A 192.168.0.0/22 (255.255.252.0) mask is a common summary for /24 networks.

DAtlanta(config-route)#area 1 range 192.168.0.0 255.255.248.0

While `area 1 range` is correct for the area ID, a 255.255.248.0 mask (indicating a /21 network) would summarize a larger block than a 255.255.252.0 mask (/22), and without specific details of the Area 1 subnets, 255.255.252.0 is a common summary for four /24 networks.

Concept tested: OSPF Inter-area Route Summarization

Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/15-s/iro-15-s-book/ospf-cfg-area-sum.html

Topics

#OSPF summarization#OSPF ABR#OSPF LSA Type 3#OSPF inter-area routing

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