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

D (Unique Local Addresses — ULA): IPv6 addresses in the FC00::/7 range, used for internal networks only, not routable over the global internet.

Ideal for campus or enterprise networks requiring internal-only addressability while avoiding conflict with global prefixes.

Why other options are incorrect:

A & B: Not valid IPv6 address types.

C: Link-local addresses (FE80::/10) are valid only for single-hop communication and cannot be routed even within the local campus.

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In MPLS networks, the MPLS header contains a 3-bit EXP (experimental) field that is used for QoS classification. Since the customer edge (CE) is managed by the service provider, it is common and best practice to map customer traffic classification (DSCP) into MPLS EXP at ingress into the MPLS core. This allows consistent QoS treatment throughout the core.

DSCP provides granular QoS markings (6-bit field, 64 values) which can be easily mapped to 3-bit EXP (8 values).

Mapping DSCP to EXP supports the 6-class model required by many service providers.

Why other options are incorrect:

A, C: IP CoS and IP precedence are legacy and not as granular as DSCP.

B: Flow-label is used in IPv6 for traffic engineering, not for MPLS QoS classification.

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Comprehensive and Detailed Explanation From Exact Extract of Design Expert (CCDE)

Summarization reduces control plane state by abstracting detailed route information. As packets move further away from the destination subnet, the network advertises summarized prefixes instead of individual host or subnet routes, minimizing control plane overhead and routing table size. This helps scale large networks and improves convergence times.

While aggregation and summarization are related, summarization specifically refers to the propagation of route prefixes and their abstraction — making it the precise fit for this question.

C (Synchronous replication over Metro Ethernet) provides real-time replication with zero data loss (RPO = 0) and minimal recovery time (RTO ≈ 0).

Metro Ethernet offers low-latency, high-bandwidth, and deterministic connectivity between closely located data centers, ideal for synchronous replication.

Why other options are incorrect:

A & D: Asynchronous replication cannot guarantee zero RPO/RTO.

B: MPLS introduces variable latency unsuitable for synchronous replication.

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For accurate location tracking in wireless networks, signal triangulation methods like RSSI, TDoA, or Angle of Arrival require:

A (Perimeter coverage): Adding APs along the perimeter improves location accuracy by minimizing blind spots and improving triangulation geometry.

B (Higher density, <40 ft spacing): Reducing inter-AP distance increases overlapping coverage, which provides more data points for accurate positioning.

Other options explained:

C: Directional antennas limit overlapping coverage, reducing triangulation accuracy.

D: Monitor mode APs can assist in location services but are secondary to proper placement and density.

E: Increasing transmit power may enlarge cell size but can decrease accuracy by reducing overlapping AP zones.

C (Scalable):For rapidly growing or contracting businesses, scalability is the highest priority to ensure that the network can adapt to changes in size, services, and demand without major redesigns.

Other options explained:

A: Hierarchical design improves structure but does not guarantee scalability.

B: Modularity aids scalability but is a design approach, not the ultimate priority.

D: A dedicated core is part of hierarchical designs but not always essential for startups.

D (Data confidentiality rules): The most critical factor in cloud service placement is data confidentiality and compliance with regulatory requirements. Certain data may not legally or contractually be permitted to leave specific geographic or organizational boundaries, directly influencing whether a public, private, hybrid, or on-premise deployment is used.

Other options explained:

A: Replication cost is important but secondary to legal and regulatory compliance.

B: Application structure affects architecture but doesn't override confidentiality restrictions.

C: Implementation time is a project management concern, not a service placement driver.

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A (Access):QoS classification and marking should occur as close to the traffic source as possible—at the access layer—so that policies can be consistently applied throughout the network.

Other options explained:

B/D: QoS policies at these layers rely on markings applied earlier.

C: Collapsed core is simply core and distribution merged, but marking should still happen at access.

D (Group Encrypted Transport VPN - GET VPN):GET VPN encrypts traffic across private WANs like MPLS while maintaining full-mesh routing visibility and offering centralized key management with minimal encapsulation overhead.

Other options explained:

A: S-VTI is used for point-to-point IPsec tunnels.

B: DMVPN is used for dynamic multipoint Internet-based VPNs.

C: MGRE is a tunneling protocol but lacks security features.

Hot-potato routing refers to the practice of routing traffic out of the network as quickly as possible—typically using the shortest IGP path to the egress point. While efficient for internal networks, it can lead to unpredictable routing behavior and suboptimal traffic paths if not coordinated with external peers.

D is correct: Without alignment between internal metrics and external relationships, hot-potato routing can result in asymmetric routing, congestion, or routing loops.

A is incorrect: Content providers often prefer cold-potato routing to control quality of service.

B describes cold-potato routing, where traffic is retained longer.

C is misleading; OSPF doesn’t define hot-potato behavior explicitly—it results from equal-cost metrics and shortest IGP paths.

Because asymmetric routing is occurring, strict uRPF (which requires the return path match) would block legitimate traffic. In this scenario, deploying uRPF loose mode is optimal:

Loose mode checks only for the existence of the source IP in the routing table, not the exact interface.

It provides protection against spoofed IP packets even if asymmetric routing occurs.

Why other options are incorrect:

A: Null0 static routes do not prevent spoofed source addresses.

B: Strict mode would incorrectly drop valid traffic due to asymmetry.

C: ACLs could help but may not scale or adapt dynamically to traffic patterns.

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B (Install firewalls):PCI DSS requires network segmentation, filtering, and perimeter defense via firewalls.

C (Use antivirus software):Malware protection and anti-virus software are mandatory on all systems interacting with cardholder data.

Other options explained:

A/D/E: These are general security best practices but not specific mandatory requirements under PCI DSS control objectives.

Comprehensive and Detailed Explanation:

B: Augmented SDN allows external applications or controllers to interact with the traditional control plane (e.g., RIB or FIB) via APIs, without fully replacing it.

A (replace) removes traditional control protocols entirely.

C (hybrid) uses both SDN and legacy control planes, but without deep integration.

D (distributed) refers to traditional decentralized control planes.

Augmented SDN enhances traditional routing with programmable control, offering near real-time visibility and dynamic response without disrupting the existing control architecture.

Comprehensive and Detailed Explanation From Exact Extract of Design Expert (CCDE)

Controller-based networks centralize control logic, abstracting hardware complexity and providing consistency. This results in:

C. Abstraction: Devices are treated as policy endpoints rather than configuration silos, simplifying network operations and scalability.

E. Consistent Configuration: Policies and configurations are pushed uniformly across all devices from the controller, reducing human error and improving compliance.

These features align with CCDE v3.1 recommendations for modern, policy-driven, and scalable architectures that are easier to manage and automate.

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C (PIM Sparse Mode with RP located at the hub):DMVPN networks typically leverage sparse mode multicast due to their efficiency in dynamic topologies. Locating the Rendezvous Point (RP) at the hub simplifies multicast state management, since the hub serves as the central aggregation point and ensures optimal rendezvous functionality without requiring complex RP placement across spokes.

Other options explained:

A: Dense mode is inefficient and generates unnecessary flooding, especially in WAN environments.

B/D: Placing RPs at remote sites introduces unnecessary complexity and operational challenges.

The hierarchical model provides:

A: Fault isolation by limiting failures to specific layers.

D: Modularity and flexibility, making it easier to implement changes without affecting the entire network.

Why other options are incorrect:

B: Design typically starts at the access layer upwards.

C: Server access is handled at the distribution or access layer, not the core.

E: Security is handled at access/distribution layers, not primarily at core layer.

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.