400-007 Exam Dumps - Cisco Certified Design Expert (CCDE v3.1)

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.

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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Comprehensive and Detailed Explanation:

C: Using dynamic routing protocols (e.g., OSPF, EIGRP, or BGP) provides real-time path selection, automatic failover, and improved resiliency. It eliminates manual reconfiguration delays associated with static routing, directly addressing user experience issues during failure.

Other options:

A: QoS improves traffic prioritization, not failover/resiliency.

B: Bandwidth upgrades do not address the failure-handling problem.

D: Adding a third link increases cost without solving the root issue—ineffective routing response.

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C (More consistent device configuration):Centralized control allows uniform policy application, eliminating configuration drift across devices.

E (Configure features at network-level rather than device-level):Controller-based networks abstract network services from individual devices, enabling network-wide configuration from a single source of truth.

Other options explained:

A: Forwarding tables still exist in both architectures.

B: Traditional networks offer per-device flexibility; controllers abstract this.

D: APIs are usually provided at controller level, not per device.

D (Root Guard): Prevents unauthorized devices from becoming the STP root by blocking superior BPDUs on access ports.

E (BPDU Guard): Immediately shuts down ports that receive unexpected BPDUs, protecting against accidental or malicious connection of switches to access ports.

Why other options are incorrect:

A: Loop Guard protects against unidirectional link failures but not unauthorized devices.

B: PortFast speeds up STP convergence on access ports but does not provide security.

C: DTF (Dynamic Trunking Protocol) is not a security feature.

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🟦QUESTION NO: 382 [Protocol Design Implications]

During IPv6 deployment in a legacy network, what must be considered for older Layer 2 switches? (Choose two)

A. If IPv6 anycast deployment is planned, then make sure that Layer 2 switches support DHCPv6 snooping

B. If IPv6 anycast deployment is planned then make sure that Layer 2 switches support ND snooping

C. IPv6 is transparent on Layer 2 switches so no changes are needed to the Layer 2 switches

D. If IPv6 multicast deployment is planned, then make sure that Layer 2 switches support MLD snooping

E. If IPv6 anycast deployment is planned, then make sure that Layer 2 switches support ICMPv6 snooping

Answer: C, D

🔍Explanation:

C: IPv6 functions at Layer 3, and Layer 2 switches (which do not inspect or modify Layer 3 headers) typically forward IPv6 frames transparently just like IPv4—unless enhanced services are needed.

D: For efficient IPv6 multicast handling (e.g., neighbor discovery, multicast services), switches should support MLD snooping (equivalent to IGMP snooping for IPv4).

Incorrect options:

A, B, E: DHCPv6 snooping, ND snooping, and ICMPv6 snooping are not standard or widely implemented features in Layer 2 devices. They're also unnecessary for basic IPv6 forwarding.

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🟦 QUESTION NO: 383 [Business-Driven Design Approaches]

Which two business areas support continuity during emergencies by understanding data flows and business processes? (Choose two)

A. Decentralized device management

B. BYOD policy

C. Disaster recovery

D. Centralized device management

E. Business continuity

Answer: C, E

🔍Explanation:

C: Disaster Recovery focuses on restoring services and data after a catastrophic event.

E: Business Continuity is a broader framework ensuring operations can continue despite disruptions. Both require knowledge of critical data flows and dependencies.

Other options:

A & D: Device management is operational—not directly focused on emergency business continuity.

B: BYOD is a policy concern related to access and security, not continuity.

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🟦 QUESTION NO: 384 [Security, Automation, and Policy Integration in Design]

Two companies want a VPN tunnel to exchange HTTP REST APIs. Only data integrity (not confidentiality) is required. Devices have limited resources.

A. GRE tunnel

B. GRE over IPsec

C. IPsec ESP

D. IPsec AH

Answer: D

🔍Explanation:

D: IPsec Authentication Header (AH) provides integrity and authentication, but not encryption. It’s ideal when data confidentiality is handled at the application layer and minimal overhead is desired.

Incorrect options:

A: GRE is a tunneling protocol, but it does not provide integrity or security.

B: GRE over IPsec is more complex and includes encryption (not needed here).

C: IPsec ESP provides encryption and integrity—overkill for this use case.

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🟦 QUESTION NO: 385 [Security, Automation, and Policy Integration in Design]

What is a key benefit of Infrastructure as Code (IaC)?

A. Declarative pipelines

B. Configuration drift

C. Agent monitoring

D. Repeatable deployments

Answer: D

🔍Explanation:

D: Repeatable deployments are one of the core benefits of IaC. It allows infrastructure to be provisioned consistently every time using version-controlled templates.

Incorrect options:

A: Declarative pipelines relate more to CI/CD processes than directly to IaC.

B: IaC helps prevent configuration drift, but drift itself is a problem—not a benefit.

C: Agent monitoring is a function of monitoring tools, not IaC.

Comprehensive and Detailed Explanation:

A: PaaS (Platform as a Service) solutions often introduce strong vendor-specific APIs, services, and tooling, making it difficult to migrate applications later—leading to vendor lock-in.

Other options:

B and C apply more to SaaS and IaaS models.

D: Multi-tenant security concerns are common in all models but not unique or predominant in PaaS.

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The scenario prioritizes:

In-house management (not managed services)

Scalability (exponential branch growth)

OPEX reduction (low operational cost)

SD-WAN over L3VPN offers a balance of:

Mid-level ISP cost (leveraging L3VPN as transport)

Centralized management and automation (ZTP, templates)

Support for segmentation, application-aware routing, and path control

Lower OPEX due to simplified configuration and monitoring

Managed SD-WAN has higher ISP and OPEX cost, and DMVPN is more manual and complex to scale. SD-WAN over L2VPN might reduce ISP cost but is less common and not optimal for rapid scalability.