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300-420 · Question #308

Refer to the exhibit. An architect is designing a Layer 3 campus network. The design must hide network instability, reduce network overhead, and conserve critical device memory. Which route…

The correct answer is B. - The core layer must advertise a default route toward the aggregation layer. To hide network instability, reduce overhead, and conserve memory in a hierarchical campus design, the core layer should advertise a default route towards the aggregation layer.

Advanced Enterprise Campus Networks

Question

Refer to the exhibit. An architect is designing a Layer 3 campus network. The design must hide network instability, reduce network overhead, and conserve critical device memory. Which route summarization solution must the architect select?

Exhibit

300-420 question #308 exhibit

Options

  • A
    • The aggregation layer must advertise a default route toward the core layer.
  • B
    • The core layer must advertise a default route toward the aggregation layer.
  • C
    • The aggregation layer must advertise a default route toward the access layer.
  • D
    • The core layer must advertise a default route toward the aggregation layer.

How the community answered

(23 responses)
  • A
    9% (2)
  • B
    83% (19)
  • C
    4% (1)
  • D
    4% (1)

Why each option

To hide network instability, reduce overhead, and conserve memory in a hierarchical campus design, the core layer should advertise a default route towards the aggregation layer.

A- The aggregation layer must advertise a default route toward the core layer.

The aggregation layer advertising a default route to the core layer is incorrect; the core layer typically needs to know all reachable networks or have its own default to external providers.

B- The core layer must advertise a default route toward the aggregation layer.Correct

By having the core layer advertise a default route towards the aggregation layer, aggregation switches only need to maintain specific routes for their directly connected networks and use the default for all other destinations, which reduces memory consumption, routing overhead, and hides instability from the larger network.

C- The aggregation layer must advertise a default route toward the access layer.

While the aggregation layer typically advertises a default route to the access layer to reduce routing tables on access devices, this option addresses a narrower scope and does not comprehensively fulfill the requirements for the overall campus network design regarding the core-aggregation interaction.

D- The core layer must advertise a default route toward the aggregation layer.

This option is identical to B and therefore correct; if presented as separate choices, it would indicate a redundant option in the question.

Concept tested: Hierarchical network summarization and default routing

Source: https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/Campus/campus_lan_design_guide/campus_lan_design.html

Topics

#Route Summarization#Default Routing#Hierarchical Network Design#Campus Network Design

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