Cisco Updated 400-007 Exam Questions and Answers by katie

C (SPF hold time): Controls the minimum amount of time between Shortest Path First (SPF) recalculations in link-state protocols like OSPF and IS-IS. This mechanism prevents frequent SPF runs due to rapid or transient topology changes, providing stability.

Other options explained:

A: Transmit delay affects LSA propagation but not routing protocol recalculation timing.

B: Throttle timers are related but primarily control LSA generation intervals.

D: Interface dampening suppresses flapping i

The hierarchical LAN design model — access, distribution, core — provides:

Scalability through structured hierarchy (A).

Easier change management and staged deployments since functions are isolated at each layer (E).

CCDE v3.1 emphasizes hierarchy for long-term scalability, manageability, and operational stability.

Why other options are incorrect:

B: Modern data centers favor spine-leaf over traditional hierarchy.

C: The model simplifies rather than complicates.

D: Simplification is not its primary advantage — scalability and modularity are.

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Policy-Based Routing (PBR) allows traffic from a specific source (172.16.2.0/24) to follow a user-defined path (via Singapore), overriding the default ECMP behavior.

This solution is optimal for traffic steering when granular control is required for specific prefixes while leaving the rest of the traffic to use default ECMP routes.

Why other options are incorrect:

B: Route summarization affects route advertisements, not traffic forwarding paths for specific prefixes.

C: Unequal-cost load balancing influences overall ECMP behavior, not source-based forwarding control.

D: Loop-Free Alternate (LFA) is for fast failover, not policy-based forwarding decisions.

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B (Cloud OnRamp):Cloud OnRamp extends SD-WAN capabilities to optimize SaaS and IaaS connectivity, offering dynamic path selection, performance monitoring, and improved user experience when migrating to cloud services.

Other options explained:

A: Describes general cloud architecture, not an SD-WAN feature.

C: Cloud registry is not an SD-WAN feature.

D: Microservices are an application architecture, not a WAN migration tool.