Cisco Updated 400-007 Exam Questions and Answers by maksymilian

BFD (Bidirectional Forwarding Detection) operates by exchanging control packets between peers, typically using UDP encapsulation. In single-hop deployments, BFD sessions are often established using:

Source IP = destination IP = local interface IP (identical source and destination addresses), especially in certain implementations like Cisco single-hop BFD.

This allows rapid fault detection without routing dependency.

The IPS must permit these packets to avoid disrupting BFD functionality.

Why other options are incorrect:

A: Fragmentation is irrelevant to BFD.

B, C, D, F: BFD does not use broadcast, multicast, or 0.0.0.0 addresses.

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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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A (Faster detection and response):Telemetry like IPFIX enables real-time network visibility and anomaly detection, significantly improving Mean Time to Detect (MTTD) and Mean Time to Respond (MTTR).

Other options explained:

B: IPFIX feeds data to incident response, but doesn't directly integrate plans.

C: IPFIX improves detection but primarily reduces response time.

D: Asset identification typically uses CMDB or inventory tools, not IPFIX alone.

Comprehensive and Detailed Explanation:

A: QoS (Quality of Service) helps preserve performance for critical applications when only one link is available by prioritizing high-value traffic. This solution works within existing infrastructure—meeting the "no additional CAPEX" requirement.

Other options:

B and C introduce new hardware or services—thus increase CAPEX.

D: Dynamic routing helps with failover but doesn't solve the bandwidth issue under failure conditions; QoS does.

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