352-001 Question #340: Real Exam Question with Answer & Explanation

Question

Options

• ASwitch routed interfaces converge faster than SVI interfaces.
• BRouting protocol timers that are tuned aggressively increase the control plane's CPU utilization.
• CLayer 3 down detection is faster than Layer 1 and Layer 2 mechanisms.
• DInterface dampening with routing protocol timers that are tuned low improve convergence time.
• EFiber cable provides faster convergence than UTP cable.

Explanation

Routed interfaces detect link failures faster than SVIs due to direct physical state dependency, and aggressively tuned routing protocol timers increase control plane CPU consumption.

Common mistakes.

• C. Physical link-down signals at Layer 1 and carrier-loss detection at Layer 2 are faster than Layer 3 protocol-based detection, which depends on timer expiration - this statement reverses the actual order of detection speed.
• D. Interface dampening suppresses route advertisements for flapping interfaces by applying an exponential penalty and hold-down period, which delays convergence rather than improving it, and conflicts with the goal of aggressively low routing timers.
• E. The physical cable medium type does not meaningfully affect Layer 3 convergence time at typical LAN and WAN distances because convergence speed is governed by protocol timer values and failure detection logic, not the signal propagation difference between fiber and UTP.

Concept tested. Layer 3 convergence - routed interfaces vs SVIs and timer CPU impact

Reference. https://www.cisco.com/c/en/us/support/docs/ip/ip-routing/13717-46.html

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