Cisco Updated 400-007 Exam Questions and Answers by andre

OSPF uses pacing timers to control how quickly it sends LSAs to neighbors to prevent network flooding and CPU spikes:

C. Retransmission-pacing timer: Controls spacing between retransmitted LSAs queued after a lost or unacknowledged transmission.

E. Flood-pacing timer: Controls spacing between consecutive LSAs when flooding new information to peers.

These timers are critical in scaling OSPF in dense or unstable topologies and are key to tuning control plane convergence performance without destabilizing routers.

Let’s calculate Total Cost of Ownership (TCO) for 24 months based on the table and given scaling requirements:

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Metro Ethernet:

CAPEX = $45,000

Installation Fee = $5,000

OPEX = $125,000/year → $250,000 for 2 years

Total = 45,000 + 5,000 + 250,000 = $300,000

DWDM:

CAPEX = $250,000

Installation Fee = $30,000

OPEX = $100,000/year → $200,000 for 2 years

Total = 250,000 + 30,000 + 200,000 = $480,000

CWDM:

CAPEX = $150,000

Installation Fee = $25,000

OPEX = $100,000/year → $200,000 for 2 years

Total = 150,000 + 25,000 + 200,000 = $375,000

MPLS:

CAPEX = $50,000

Installation Fee = $75,000

OPEX = $150,000/year → $300,000 for 2 years

Total = 50,000 + 75,000 + 300,000 = $425,000

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Metro Ethernet clearly results in the lowest total cost while meeting dual 10G and scalable growth to 20 connections due to its simple provisioning and operational flexibility.

This approach fully aligns with CCDE v3.1 business-driven cost modeling principles: balancing cost, scalability, and operational simplicity.

Why other options are incorrect:

B, C, D: All are more expensive after full 2-year calculation for the required scale.

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Comprehensive and Detailed Explanation:

B: Augmented SDN allows external applications or controllers to interact with the traditional control plane (e.g., RIB or FIB) via APIs, without fully replacing it.

A (replace) removes traditional control protocols entirely.

C (hybrid) uses both SDN and legacy control planes, but without deep integration.

D (distributed) refers to traditional decentralized control planes.

Augmented SDN enhances traditional routing with programmable control, offering near real-time visibility and dynamic response without disrupting the existing control architecture.