Free Cisco 400-007 Practice Exam with Questions & Answers | Set: 8

A: The overload bit (OL bit) signals other routers to avoid using the overloaded router as a transit path for Level 2 traffic. However, the overloaded router can still forward Level 1 local area traffic if applicable.

D: The overload bit is commonly used during router bootup to prevent temporary black holes while the router completes its routing protocol convergence and LSDB synchronization.

Why other options are incorrect:

B: CSNP prioritization is not related to overload bit functionality.

C: LSDB synchronization occurs through normal IS-IS mechanisms; overload bit is not involved.

E: The overload bit prevents transit usage, not attracts traffic.

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Comprehensive and Detailed Explanation:

To reduce oscillation and improve resiliency:

D: Increasing unequal-cost multipath (UCMP) paths allows the routing protocol to load-share over more than one path, preventing traffic congestion from oscillating between nodes.

E: Dual links to each site improve bandwidth and failover options, reducing reliance on overloaded peers.

Other options:

A: Increasing redundant paths may worsen convergence complexity and doesn't solve oscillation.

B: Removing inter-spoke links reduces redundancy.

C: Increasing convergence timers delays recovery and stability.

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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 (PPDIOO - Prepare, Plan, Design, Implement, Operate, Optimize):PPDIOO is Cisco’s structured lifecycle methodology designed specifically for network design, deployment, and management. It ensures continuous improvement, iterative design, and aligns technical efforts with business goals throughout the entire network lifecycle.

Other options explained:

B: Waterfall is a generic software development methodology.

C: Spiral emphasizes iterative risk management for software development.

D: V model applies primarily to software verification and validation.

B (Software as a Service - SaaS):SaaS provides end users with complete applications hosted and managed by third-party providers, accessed via web interfaces.

Other options explained:

A: PaaS provides platforms for application development, not complete applications.

C: IaaS provides compute/storage resources but not full applications.

D: WaaS (Workspace as a Service) is a niche model, not generally used as standard SaaS definition.

Unicast Reverse Path Forwarding (uRPF)is a security feature that helps mitigate IP spoofing attacks. It checks whether the source of a packet received on an interface matches the best return path to that source in the routing table.

Strict Mode (C):Ensures the source IP address of a packet is reachable via the same interface on which the packet was received. This prevents forged source IP addresses from traversing the network, which is essential in defending against outbound DDoS attacks sourced from infected hosts.

Loose Mode (B):Only verifies that the source IP exists in the routing table (less strict), which might still allow spoofing in multi-homed or asymmetric environments.

uRPF strict mode is the best fit in secure environments with symmetric routing—commonly in enterprise edge or distribution layers.

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The scenario requires controlling how AS 111 sends its outbound traffic (egress traffic). BGP policy control for outbound traffic is best handled via manipulating the BGP Local Preference attribute, as:

Local Preference (LocalPref) influences path selection for outbound traffic by setting a preference for one path over another.

It is evaluated within the AS and does not require coordination with external autonomous systems.

LocalPref changes are fully contained inside AS 111 and satisfy the requirement to only affect AS 111.

A higher Local Preference value is preferred, thus you set higher values for routes learned via AS 100.

Why other options are incorrect:

A (community): Typically influences inbound traffic or interacts with upstream providers.

B (MED): Influences inbound traffic for external neighbors, not outbound.

D (AS Path): Also primarily influences inbound traffic selection by remote ASes.

In infrastructure design, primary constraints are:

D (Component availability): If hardware or software components are not readily available, designs may need to adapt.

E (Total cost): Budget limitations always influence design decisions regarding redundancy, scalability, and technology selection.

Why other options are not primary constraints:

A: Monitoring is a design consideration, but not a core constraint.

B: Time frame impacts project delivery, not necessarily the design robustness.

C: Staff experience affects operations but is not a primary technical design constraint.

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The Host Subinterface in Control Plane Protection (CPPr) protects traffic destined to the router itself (e.g., routing protocols, management traffic).

This is critical in preventing DoS or CPU exhaustion attacks targeting control plane services directly.

Why other options are incorrect:

B: Main interface refers to the global control plane policy but lacks the granularity.

C: Transit subinterface protects transit traffic handled by the forwarding plane.

D: CEF-exception handles non-IP or exception traffic, not regular control plane IP traffic.

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