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

B (Control plane is unavailable):In centralized SDN models where the controller has full exclusive configuration authority (lock), controller failure results in loss of control-plane functionality. No new flows can be programmed, and dynamic traffic adjustments cannot occur until the controller is restored.

Other options explained:

A: Devices typically continue forwarding existing flows but are not in read-only config mode.

C: Backups may still be available independently.

D: Manual changes are often restricted to preserve state consistency.

Increasing jitter buffer size smoothens jitter but at the cost of introducing additional delay.

Excessive jitter buffering can lead to perceptible audio or video lag, impacting user experience.

C: Therefore, the undesired effect is increased transport delay, potentially leading to quality issues if the buffer size is too large.

Why other options are incorrect:

A and D: Jitter buffering does not improve jitter itself; it masks it at the expense of delay.

B: Jitter compensation doesn ' t increase jitter, but delay.

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Security design must be aligned with:

Business objectives (A): Security design must meet business needs without hindering operations.

Security policies and standards (B): Compliance with internal and external regulations is mandatory.

CCDE v3.1 teaches that security design always starts from business intent and policy compliance, not purely technical or scope-based factors.

Why other options are incorrect:

C and D: Security design applies to all environments, not just multi-site or new deployments.

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C (Faster convergence): 802.1s (Multiple Spanning Tree Protocol – MSTP) improves convergence times over legacy 802.1D (STP) and PVST+ by leveraging the rapid convergence benefits of 802.1w (RSTP).

E (Maps multiple VLANs): MST allows multiple VLANs to share the same spanning-tree instance, reducing the overall number of instances required and improving scalability.

Other options explained:

A: The standard supports 64 MST instances, not 1024.

B: 802.1w (RSTP) is the basis for 802.1s; Cisco’s proprietary enhancement was originally PVST+.

D: MST actually reduces CPU/memory compared to running multiple instances of PVST+.

NETCONF (Network Configuration Protocol) is a standardized protocol used for automating configuration and management of network devices. According to IETF standards (RFC 6241), the required encoding for NETCONF is:

XML (Extensible Markup Language)

Cisco IOS XE supports NETCONF over SSH and uses XML to structure both configuration data and RPC messages. XML allows strict schema validation (via YANG models), extensibility, and rich hierarchical structure required for modern network automation.

Other formats:

HTML is not a data encoding method.

YAML is typically used with configuration management tools, not NETCONF.

JSON is supported in RESTCONF, not in traditional NETCONF.

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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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When multiple virtualized network zones (such as VRFs, virtual firewalls, or logical partitions) are consolidated onto a single physical device, the primary concern is:

A (Fate sharing): A single hardware failure, software crash, or resource exhaustion event could simultaneously impact all virtualized zones, creating a shared risk across multiple otherwise isolated services.

Other options explained:

B: CPU resource allocation can be controlled via resource management but is not the primary risk.

C: Congestion control is typically a traffic engineering issue, not a virtualization risk.

D: Security isolation can be maintained through proper virtualization boundaries.

E: Bandwidth can be managed through QoS and resource allocation.

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