Cisco
352-001 · Question #253
352-001 Question #253: Real Exam Question with Answer & Explanation
The correct answer is C: Use IS-IS mesh groups.. IS-IS mesh groups reduce unnecessary LSP flooding in fully meshed topologies by restricting which interfaces retransmit received LSPs, eliminating redundant floods across a dense core.
Question
Refer to the exhibit. A service provider using IS-IS has designed this network with all core links at the Layer 2 control plane. How will they adjust the design to reduce the flooding of update packets?
Exhibit
Options
- AChange the area type of the links to be level-1-2 to allow level-1 updates.
- BChange the network type of the links from broadcast to point-to-point.
- CUse IS-IS mesh groups.
- DConfigure SPF timers to be more aggressive so that updates are more quickly cleared from the queue.
Explanation
IS-IS mesh groups reduce unnecessary LSP flooding in fully meshed topologies by restricting which interfaces retransmit received LSPs, eliminating redundant floods across a dense core.
Common mistakes.
- A. Changing links from Level 2 to Level 1-2 introduces Level 1 area flooding in addition to Level 2 flooding, which increases LSP update traffic rather than reducing it.
- B. Changing the network type from broadcast to point-to-point eliminates the DIS election and pseudonode LSPs but does not address the core problem of redundant LSP retransmission across many interfaces in a mesh.
- D. Aggressive SPF timers control how quickly the shortest-path-first calculation runs after an LSP is received - they affect computation scheduling, not the volume or propagation of LSP flood packets across the network.
Concept tested. IS-IS mesh groups reducing LSP flooding in dense topologies
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