Cisco Updated 400-007 Exam Questions and Answers by vivienne

This scenario describes a centralized control mechanism where:

The SDN controller learns the network topology using BGP Link-State (BGP-LS).

The controller installs control-plane policies using protocols like PCEP or BGP.

Policies are pushed centrally and result in new RIB entries at the routers.

This is the hallmark of a centralized SDN architecture:

The controller has a global view and decision-making logic.

Routers remain relatively simple in the control plane and act on instructions.

This aligns with CCDE v3.1 under the “Technology Comparisons and Use Cases” topic, where SDN models are compared:

Centralized SDN (controller-driven)

Distributed SDN (traditional)

Hybrid (a blend of both, which is not represented here)

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Interface dampening is primarily designed to suppress rapid, repetitive interface flaps (high-frequency short-duration flaps), which can cause instability in routing protocols and excessive reconvergence events.

When many brief interface failures happen, dampening delays the routing protocol’s reaction until the interface remains stable.

This helps prevent control-plane churn in fast-converging designs.

This approach is emphasized in CCDE v3.1 design principles where balance between stability and convergence is required.

Why other options are incorrect:

A: Occasional long-duration flaps don’t require dampening.

C & D: Hardware speed mismatches are better handled by carrier-delay or debounce-timer mechanisms, not dampening.

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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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