400-007 Cisco Certified Design Expert (CCDE v3.1) Free Practice Exam Questions (2025 Updated)

A: Flow-based analysis allows understanding bandwidth usage across apps and sessions, crucial for voice/video capacity management.

C: Call management systems track CAC and call quality failures, key for voice/video troubleshooting.

D: Active synthetic probes proactively inject traffic to monitor loss, latency, and jitter under real-time conditions.

Why other options are incorrect:

B: Network convergence is not directly analyzed through call management tools.

E: Passive synthetic probes is not an accurate term; passive monitoring refers to analysis of real traffic flows, not synthetic tests.

F: PTP time-stamping is more applicable to clock synchronization, not regular voice/video performance monitoring.

When Bidirectional Forwarding Detection (BFD) is not available, OSPF can still achieve subsecond convergence using the OSPF fast hello feature.

Fast hello allows the configuration of OSPF hello/dead intervals to subsecond values (e.g., hello = 100ms, dead = 300ms).

This accelerates OSPF’s ability to detect neighbor failures based on missed hello packets without relying on external mechanisms like BFD.

Why other options are incorrect:

A. STP (Spanning Tree Protocol) is unrelated to OSPF and is used at Layer 2.

C. LFA (Loop-Free Alternate) is a fast reroute technique but does not affect neighbor failure detection.

D. DPD (Dead Peer Detection) is used in VPN technologies (e.g., IPsec) and not applicable in OSPF.

Fast hello is fully aligned with CCDE v3.1 under “Protocol Design Implications” and is a commonly recommended method for improving IGP convergence performance when BFD is not an option.

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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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IPv6 multicast supports two key mechanisms for Rendezvous Point (RP) discovery:

A. Embedded RP: The RP address is embedded within the multicast group address (ff70::/12). This allows automatic RP discovery by routers and eliminates the need for signaling protocols.

C. BSR (Bootstrap Router): Used in IPv6 as a replacement for Auto-RP (which is IPv4-specific), BSR dynamically announces the RP to multicast routers in the domain.

Other options:

B. MSDP: Not supported in IPv6 multicast since source registration and discovery are handled differently.

D. Auto-RP: IPv4-specific and not supported in IPv6.

E. MLD: Manages listener (receiver) membership, not RP discovery.

A: FabricPath assigns a specific multicast (S,G) flow to one tree. A single (S,G) does not get load-balanced across multiple trees.

E: Overall multicast traffic across multiple (S,G) groups is distributed across multiple FabricPath trees, providing general load balancing and efficient link utilization across the fabric.

Why other options are incorrect:

B: Traffic load per tree may not be uniform due to different group distributions.

C: The assignment is done by the ingress switch based on hashing, not all leaf nodes assign the same tree.

D: Individual (S,G) flows do not get load-balanced across trees.

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B (Point-to-multipoint network type): OSPF point-to-multipoint allows the hub to see the DMVPN topology correctly without complex neighbor relationships.

E (Set spokes priority to 0): Ensures the hub always becomes DR, maintaining predictable OSPF adjacency behavior.

Other options explained:

A: Broadcast mode is inefficient and unnecessary in DMVPN designs.

C: Mixed network types complicate adjacency maintenance.

D: Manually setting the hub priority is redundant when spokes are at priority 0.

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Software-Defined Networking (SDN) architecture is based on the logical decoupling of the control and data planes. According to the SDN reference model, the architecture typically includes the following planes:

Control Plane: This resides in the SDN controller and is responsible for decision-making, including route and policy calculations.

Application Plane: This layer contains business and network applications (e.g., firewalls, QoS policies) that communicate with the controller to request services and enforce policy.

These planes are essential in SDN architecture:

The control plane programs the forwarding behavior of network elements.

The application plane interacts via northbound APIs to define intent and service logic.

Options such as “Software plane” and “Network plane” are vague or not used in the SDN context. The “Management plane” is a separate functional layer and is not part of the architectural definition core to SDN as per CCDE v3.1.

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A soft failure refers to a condition where the network continues to operate, but performance or behavior is degraded in a way that is not immediately visible or detectable—this includes suboptimal routing, misconfigured protocols, or resource inefficiencies. These are harder to define and detect because they don't cause total outages but still impact user experience or service quality. In contrast, hard failures like outages (Option D) are more visible and measurable.

This aligns with CCDE v3.1’s guidance on resilience, observability, and performance-aware design, emphasizing proactive identification of non-fatal but service-impacting anomalies.

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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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B (Proactive network management):Network optimization involves ongoing monitoring, trend analysis, and proactive maintenance to prevent issues before they impact performance.

D (Network health maintenance):Optimization focuses on ensuring consistent network performance, reducing bottlenecks, and maintaining network integrity through regular health checks and adjustments.

Other options explained:

A: High availability is a design goal but not optimization itself.

C: Redesign suggests a major rearchitecture, not part of ongoing optimization.

E: Requirement identification happens during initial design phases.

B (Layer 3 MPLS VPN hub and spoke):A hub-and-spoke MPLS VPN allows scalable branch-to-data-center communication with efficient routing, simplified management, and adequate support for real-time video across 200 branches.

Other options explained:

A: DMVPN is flexible but not as scalable or deterministic for 200-site enterprise video conferencing.

C: VPLS operates at Layer 2 and may introduce unnecessary broadcast domain scaling challenges.

D: Full mesh MPLS is difficult to manage for such a large number of sites.

C: Serialization delay is the time it takes to place a packet onto the physical medium.

E: It is calculated as (packet size / link speed), thus depending on both the packet size and the interface speed.

Why other options are incorrect:

A: It depends on both size and line rate, not just line rate.

B: Packet type has no effect on serialization delay.

D: It's not only packet size, but also link speed that affects it.

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A (TRILL - Transparent Interconnection of Lots of Links):TRILL enables multipathing at Layer 2, eliminating classic STP blocking, allowing all uplinks to be active simultaneously, and uses IS-IS based control plane for conversational MAC learning.

Other options explained:

B: LISP operates at Layer 3 for endpoint mobility, not Layer 2 multipathing.

C: MSTP still blocks some links under normal operation.

D: Switch stacking merges multiple physical switches into one logical switch but does not provide true multipathing across independent switches.

B (Northbound APIs):Northbound APIs allow applications to communicate with the SDN controller to express service requests and provide policy intent. The controller translates these into instructions for the underlying infrastructure.

Other options explained:

A: Southbound APIs connect controllers to forwarding devices.

C: Orchestration coordinates workflows across domains but doesn’t directly connect applications to controllers.

D: The SDN controller receives the northbound API calls but is not the API itself.

B: In transparent mode, the firewall operates at Layer 2 and can participate in STP to avoid loops.

C: Multicast traffic can traverse the firewall if allowed through transparent bridging rules.

Why other options are incorrect:

A: Transparent mode requires no change to IP addressing.

D: Transparent firewalls do not form routing adjacencies.

E: Routed mode firewalls operate at Layer 3; transparent mode does not insert router hops.

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B (Reduce config complexity):Central controllers abstract policies, simplifying configuration.

C (Centralized IT functions):Controllers centralize management, automation, analytics, and assurance.

Other options explained:

A: Licensing varies but not universally inflated.

D: Failures are dependent on hardware design, not controller presence.

E: SDN does not inherently increase bandwidth usage.

D (Python):Python is widely used for network automation, configuration management, and scripting tasks. It simplifies repeatable network changes, validation, and integration with controllers and APIs, reducing deployment time.

Other options explained:

A: LISP is a routing protocol, not an automation tool.

B: Java is a general-purpose language but not commonly used for network automation.

C: "Conclusion" is not a tool.

Software-defined network segmentation is a core element of secure cloud architecture models.

It isolates workloads, minimizes blast radius, and enforces east-west security controls in dynamic multi-tenant environments.

Why other options are less appropriate:

A: This is a principle of least privilege (IAM) but not a cloud architecture characteristic.

B: Dedicated workstations are endpoint measures, not architecture-level.

C: MFA protects identity but does not define architecture segmentation.

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