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

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When a service provider does not support multicast over their Layer 3 VPN, the enterprise can useGRE tunnels between Customer Edge (CE) devicesto transport multicast traffic. This method allows the customer to encapsulate multicast packets in unicast GRE packets, which are routable through the provider’s non-multicast core.

In this scenario, the most scalable and immediate solution is to establish a GRE tunnel betweenC2 (in the head office CE router path)andC4 (at the branch office). This setup ensures that multicast traffic originating at the head office is tunneled directly to the multicast receivers, bypassing the service provider’s non-multicast-aware core.

This strategy is directly aligned with CCDE v3.1 principles, which emphasize:

Minimizing service provider dependency

Providing a scalable, customer-controlled overlay solution

Ensuring protocol compatibility across domains

Why other options are incorrect:

A: Tunnel between CE1 and CE2 is less optimal, as it may not originate or terminate at the exact multicast endpoints.

C: Tunnel between C1 and C4 is less aligned with CE-to-CE design expectations and may bypass required edge security/policy controls.

D: 2547oDMVPN is more complex and intended for full-scale VPN overlays, not quick multicast solutions.

E: Draft Rosen requires service provider support, which is currently unavailable, hence not a valid short-term option.

This solution ensures operational simplicity and future scalability with minimal provider dependency, which are core principles outlined in the CCDE v3.1 design methodology.

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 (Queue thresholding on the host subinterface):Protects CPU resources by limiting the amount of control plane traffic destined to the router itself.

E (Port filtering on the host subinterface):Allows fine-grained filtering of control plane traffic based on specific protocols or ports, protecting sensitive processes like routing protocols or management access.

Other options explained:

A, B, C: Transit subinterfaces protect forwarding plane transit traffic, not traffic destined to the control plane.

A (Roaming delay):Voice requires seamless roaming with minimal handoff delay to avoid call drops.

B (Uniform radio coverage):Consistent signal coverage is essential for maintaining voice call quality throughout the facility.

Other options explained:

C: High channel utilization affects capacity but not directly the initial readiness assessment.

D: Latency is important but typically captured during ongoing performance testing, not pre-assessment.

E: TX power changes indicate instability but are not primary readiness criteria.

A (Additional host routes):Spoke-to-spoke dynamic tunnels in DMVPN phase 3 result in OSPF populating routing tables with multiple /32 host routes for each spoke-to-spoke tunnel, which can impact scalability and routing table size.

Other options explained:

B: Priority changes not typically required.

C: Split-horizon issue is solved in DMVPN phase 3.

D: Spokes dynamically register with the hub; no manual spoke IP configuration needed.

Cisco NFVi (Network Function Virtualization Infrastructure) solutions integrate with Red Hat’s virtualization stack using:

C. Cisco Nexus switches: Provide data center network fabric.

D. Cisco UCS: Provides the compute platform for NFV workloads.

F. Cisco Virtual Network Functions: The software-based network functions running on NFVi (e.g. virtual routers, firewalls, etc.).

Why other options are incorrect:

A: Cisco Prime Service Catalog is a management tool, not part of NFVi infrastructure.

B: Cisco Open vSwitch is not a Cisco product (Open vSwitch is open-source).

E: Cisco Open Container Platform is not part of the NFVi reference solution in conjunction with Red Hat.

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C (Transparent firewall): Operates at Layer 2, allowing filtering and inspection of traffic within the same subnet without requiring IP routing changes. It performs deep packet inspection while maintaining Layer 2 adjacency, making it ideal for intra-subnet traffic control in data centers.

This allows security segmentation inside broadcast domains, enforcing security policies even for east-west traffic.

Other options explained:

A: Routed firewalls require subnet boundaries and are not ideal for intra-subnet control.

B: VLAN ACLs provide basic filtering but lack deep packet inspection capabilities.

D: Zone-based firewalls are primarily designed for inter-subnet (Layer 3) traffic segmentation.

A (Evaluate bandwidth utilization and connection quality):Before VoIP deployment, a readiness assessment must include bandwidth analysis, latency, jitter, and packet loss to ensure call quality.

Other options explained:

B: DID lines relate to telephony features but not network readiness.

C: Session table limits are unrelated to VoIP readiness.

D: Anomaly detection is security-related, not core network readiness.

To achieve sub-50 millisecond convergence after a link or node failure, the design must rely on precomputed protection paths and local repair mechanisms in the data plane. The following mechanisms meet this requirement:

B. Ti-LFA (Topology Independent Loop-Free Alternate): A next-generation fast reroute method used in Segment Routing. It offers local protection by computing loop-free backup paths that are independent of the specific failure type (node or link). It's capable of sub-50 ms convergence by rerouting traffic immediately on failure.

D. MPLS-FRR (Fast Reroute): A traditional mechanism in MPLS networks that provides pre-signaled backup Label Switched Paths (LSPs). It enables fast switchover upon failure detection—also under 50 ms.

Other options:

A. BFD: Provides fast failure detection, but does not provide the actual traffic reroute mechanism.

C. Minimal BGP scan time: Impacts control plane responsiveness but not sub-50 ms convergence.

E. IGP fast hello: Improves failure detection but alone doesn’t guarantee traffic reroute under 50 ms.

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The hub CE router is receiving IP SLA probes from all spokes, processing and responding to every request. As more spokes are added, the CPU workload on the hub increases exponentially due to:

Processing incoming IP SLA packets.

Generating and transmitting responses.

Monitoring CPU utilization at the hub ensures early detection of processing bottlenecks that could impact SLA accuracy and overall performance — a core CCDE v3.1 business-driven design consideration in centralized measurement architectures.

Why other options are incorrect:

A & B: Spoke resources are minimally taxed.

D: Buffer usage isn't the main limiting factor for IP SLA responsiveness.

C (Transparent firewalling):Transparent (Layer 2) firewalls operate at the data link layer and allow segmentation and inspection of intra-VLAN traffic without requiring changes to the existing IP addressing. This is ideal for legacy environments where IP addresses are hard-coded, while still providing fine-grained security policies between applications in the same subnet.

Other options explained:

A: Perimeter firewalls cannot segment east-west traffic within a VLAN.

B: VACLs provide basic filtering but are not as scalable or flexible as transparent firewalls for stateful inspection.

D: Routed firewalls require Layer 3 boundaries, which would conflict with hard-coded IP design.

B (Platform as a Service – PaaS): In a PaaS model, the cloud provider manages the operating system, middleware, runtime, and platform stack. The customer is only responsible for deploying and managing the application itself.

This abstraction allows developers to focus on application logic without worrying about the infrastructure or platform details.

Other options explained:

A (IaaS): Customer manages OS, middleware, and runtime; provider manages hardware and virtualization.

C (SaaS): Customer simply consumes the application; all layers are managed by the provider.

D (BMaaS): Bare Metal as a Service — customer has full control over hardware and all software layers.

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Inbound traffic engineering is best controlled by manipulating how external ASes view your routes.

AS path prepending on the 91.7.0.0/16 prefix towards AS 200 makes AS 500 prefer the less-prepended path through AS 100.

This allows granular inbound control for that specific prefix while leaving the rest of the traffic unchanged.

Why other options are incorrect:

B: Extended community is not used for direct inbound path manipulation.

C: Local preference affects outbound traffic, not inbound path selection by remote ASes.

D: MED is only compared between the same AS; it won't affect AS 500's choice.

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Performance management is the FCAPS function responsible for collecting statistics, monitoring utilization, identifying performance degradation, and optimizing network responsiveness.

It ensures that the network maintains SLA targets.

Why other options are incorrect:

A: Fault management detects and responds to failures.

B: Accounting tracks resource usage.

D: Security handles access and policy enforcement.

Comprehensive and Detailed Explanation:

B: The IPsec anti-replay mechanism protects against packet injection and replay attacks by rejecting packets outside the anti-replay window. Increasing the anti-replay window (e.g., to 4096) allows legitimate packets with slightly reordered or delayed sequence numbers to be accepted—especially critical during bursts or with asymmetric paths.

Other options:

A: QoS marking does not prevent replay.

C: Tunnel keyword restrictions don't address replay attacks.

D: Shaping affects traffic rate, not sequence validation.

D (Route maps with tags): When redistributing between OSPF domains at multiple locations (mutual redistribution), route tagging is a key technique to prevent routing loops. Each ASBR applies route tags on incoming routes, and redistribution policies check these tags to prevent re-advertising routes that originated from the other domain.

Other options explained:

A: Virtual links are for connecting discontiguous OSPF areas, not preventing redistribution loops.

B: Router ID uniqueness is required but does not prevent loops.

C: External type 2 redistribution doesn't inherently prevent loops.

A modular, scalable network design aims to:

Localize faults

Reduce impact radius of failures

Enable automated fault detection and recovery

The primary operational driver is to reduce the need for manual intervention during failures, which translates to:

Faster recovery times

Consistency in troubleshooting

Improved service reliability

While minimizing app downtime (B) is a goal, it is a result of reducing human-required failure recovery. Option C is a business process goal, and D is an architectural challenge, not an operational driver.

This aligns with CCDE v3.1's “Network Architecture Principles” for building operationally resilient networks.

🟦QUESTION NO: 374 [Business-Driven Design Approaches]

Organic growth or decline affects network demands over time. Which tool helps in designing and operationalizing networks under changing conditions?

A. Change management

B. Modularity

C. Mobility

D. Monitoring

Answer: B

🔍Explanation:

B: Modularity is a core principle of scalable network design. It allows the network to grow or shrink in response to organic changes in business demand, supporting agility, easier management, and minimal disruption during change.

Other options:

A: Change management is about documenting and approving changes—not a design principle.

C: Mobility refers to user/device flexibility, not structural adaptability.

D: Monitoring detects changes but doesn’t help design the network.

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🟦 QUESTION NO: 375 [Protocol Design Implications]

Company XYZ uses OSPF over redundant paths. What effect does BFD have during a link failure?

A. It would drop the dead peer detection time to a single hello

B. It would keep an alternate path ready in case of a link failure

C. It would optimize the route summarization feature of OSPF

D. It would detect that the neighbor is down in a subsecond manner

Answer: D

🔍Explanation:

D: BFD (Bidirectional Forwarding Detection) provides subsecond failure detection that is significantly faster than standard OSPF dead timers. When integrated with OSPF, it enables rapid neighbor failure detection, thus speeding up convergence.

Other options:

A: “Single hello” is not a valid BFD metric.

B: BFD does not influence path availability—it only detects failures quickly.

C: BFD doesn’t interact with summarization.

🟦QUESTION NO: 376 [Security, Automation, and Policy Integration in Design]

What two elements are critical for security and compliance in hybrid cloud environments? (Choose two)

A. Cloud integration and data security

B. Tighter controls based on dynamic policy enforcement

C. Security event and data interoperability

D. Flexible controls based on policy application

E. Orchestration and cross-cloud access security

Answer: C, E

🔍Explanation:

C: Security event and data interoperability ensures that logs, alerts, and policies can be analyzed across different platforms (private and public clouds), which is vital for compliance and response.

E: Hybrid clouds require secure orchestration across multiple cloud domains, including federated identity, access control, and monitoring across cloud boundaries.

Other options:

A: Too broad; integration is not specific to security/compliance.

B and D: These relate to policy enforcement but don’t directly address interoperability or compliance across multiple clouds.

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🟦 QUESTION NO: 377 [Security, Automation, and Policy Integration in Design]

To protect against future perimeter breaches, which two design options can help? (Choose two)

A. Microzoning

B. Segmentation

C. Domain fencing

D. Virtualization

E. Microperimeters

Answer: B, E

🔍Explanation:

B: Segmentation isolates network zones (e.g., separating finance from guest access), limiting lateral movement after a breach.

E: Microperimeters apply security controls closer to the application or workload, providing granular control and defense in depth.

Other options:

A: Microzoning is not a widely defined or standard practice in network security.

C: Domain fencing is not a standard security term or methodology.

D: Virtualization is a technology, not a security architecture.

🟦QUESTION NO: 378 [Network Architecture Principles]

A customer is migrating from a traditional Layer 2 data center to a VXLAN spine-leaf SDN architecture. Applications cannot be readdressed, and migration must occur incrementally. How should the legacy and new networks be connected?

A. via Layer 3 links to border leaf switches

B. via a Layer 2 trunk and Layer 3 routed links to border leaf switches

C. via a Layer 2 trunk and Layer 3 routed links to spine switches

D. via a Layer 2 trunk to border leaf switches

Answer: D

🔍Explanation:

D: A Layer 2 trunk to the border leaf allows seamless VLAN extension between the legacy Layer 2 domain and the VXLAN-based fabric. This supports application migration without readdressing. Border leaf switches are used to bridge the traditional and VXLAN segments while maintaining MAC learning and VLAN consistency.

Incorrect Options:

A & B: Layer 3 links alone would require readdressing or routing, violating the constraint.

C: Spine switches typically do not handle VLAN bridging or policy enforcement directly.

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🟦 QUESTION NO: 379 [Business-Driven Design Approaches]

Scrum and Kanban are Agile methodologies. In which two scenarios is Kanban more appropriate? (Choose two)

A. acquisition of automation tools

B. carrier lead times

C. network configuration design

D. physical hardware deployment

E. logical topology deployment

Answer: B, D

🔍Explanation:

B: Kanban is suited for environments with variable lead times, such as carrier provisioning, where tasks arrive irregularly and are processed continuously.

D: Physical hardware deployment is dependent on availability and external logistics—Kanban helps manage such workflows where task durations are less predictable.

Incorrect Options:

A: Tool acquisition is typically a one-off project rather than a workflow suited for Kanban.

C & E: These are better suited for Scrum when planning sprints and structured deployments.

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🟦 QUESTION NO: 380 [Security, Automation, and Policy Integration in Design]

The network has high CPU usage due to excessive inbound traffic impacting the control and management planes. What should be implemented?

A. control plane policing

B. deep interface buffers

C. TCAM carving

D. modular QoS

Answer: A

🔍Explanation:

A: Control Plane Policing (CoPP) protects the control plane by rate-limiting or dropping unnecessary or malicious traffic destined for the CPU. This is essential in preventing routing and management plane starvation under high traffic conditions.

Incorrect Options:

B: Deep buffers help in data plane congestion, not control plane CPU usage.

C: TCAM carving relates to hardware forwarding table allocations, not CPU protection.

D: Modular QoS is valuable for traffic shaping but not specific to control plane protection.

OSPF throttling timers control the pacing and frequency of SPF calculations and LSA generation. They help strike a balance between fast convergence and control-plane stability. The key timers include:

LSA generation throttling (min/max interval between LSA originations)

SPF calculation throttling (delays between consecutive SPF runs)

By tuning these timers, network designers can:

Prevent CPU overload caused by rapid or repeated LSA updates due to flapping links

Smooth out instability while still enabling responsive convergence

This approach aligns with CCDE v3.1 under “Protocol Design Implications” for optimizing IGP behavior in large, dynamic topologies.

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In IPv6, routers advertise prefixes via Router Advertisement (RA) messages. An attacker could inject rogue RAs to manipulate the IPv6 configuration of endpoints.

Router Advertisement Guard (RA Guard) blocks unauthorized RA messages from being received on access ports, preventing endpoints from receiving incorrect IPv6 prefixes from malicious or misconfigured devices.

This security feature is crucial when devices have IPv6 enabled but the network is IPv4-only.

Other options explained:

A: Source Guard and Prefix Guard enforce valid address and prefix assignment but do not prevent RA spoofing directly.

C: Prefix Guard focuses on controlling prefixes being assigned, not blocking RA messages.

D: Secure Neighbor Discovery (SEND) provides cryptographic protection but is rarely deployed due to complexity.

A (Focus on the solution instead of the problem): While resolving issues quickly is important for operations, solution-oriented thinking during the design phase may overlook essential requirements analysis. Design decisions must be based on problem understanding, traffic analysis, and actual network behavior.

Other options explained:

B, C, D: All directly impact WAN design by influencing QoS, capacity planning, flow optimization, and visibility.

D: CWDM (Coarse Wavelength Division Multiplexing) shares parts of the same optical transmission window (1260–1625 nm) as DWDM but uses wider spacing between channels (typically 20 nm apart).

E: CWDM typically uses passive devices (multiplexers and demultiplexers) that require no electrical power, making deployment cost-effective.

Incorrect Options:

A: CWDM is better suited for shorter distances (up to ~80 km) and doesn't typically use optical amplifiers (EDFA). DWDM is better for long-haul with amplification.

B: 850 nm is used in multimode fiber systems (not CWDM).

C: CWDM supports up to 18 channels; DWDM supports up to 32 or more.

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B (MPLS over BGP over mGRE):This design allows enterprises to run MPLS VPNs across their own infrastructure (Overlay VPN) while using MP-BGP for control plane distribution of VPNv4 routes. The mGRE tunnel structure allows scalability as branches grow, while MPLS VPN labels ensure traffic separation.

Other options explained:

A: EIGRP OTT is not scalable for large VPN deployments.

C: DMVPN per VRF becomes complex with high scale growth.

D: Point-to-point GRE per VRF lacks scalability for 60+ sites.

In a standard 3-tier data center architecture (access, aggregation, core), the Layer 2-to-Layer 3 boundary typically resides at the aggregation layer. When extending VLANs between data centers using a Layer 2 interconnection, the most optimal and scalable termination point is at the aggregation layer because:

It naturally handles VLAN demarcation and Layer 3 boundary.

Spanning Tree Protocol (STP) domains remain contained within local aggregation blocks.

The core remains Layer 3-only, ensuring scalability, stability, and no STP involvement.

Simplifies traffic engineering, FHRP operations, and minimizes control-plane complexity across sites.

This design is consistent with CCDE v3.1 best practice where VLAN extension is isolated to aggregation to avoid STP scaling issues and maintain hierarchical design principles.

Why other options are incorrect:

A: STP isolation can still be achieved at aggregation while keeping the core Layer 3.

C: Access layer extensions would increase STP scope and complexity unnecessarily.

D: Core termination violates Layer 3 core design, bringing STP into the core, which is not scalable.

D (LISP — Locator/ID Separation Protocol):

Supports massive scale with centralized control plane (mapping servers).

CE routers do not run routing protocols with PE.

Allows load balancing and multi-homing using locator sets.

Supports IPv4 and IPv6.

Lightweight CE requirements fit low-cost platforms.

Why other options are incorrect:

A: FlexVPN is control-plane intensive and less scalable for large managed CE deployments.

B: Point-to-point GRE doesn't scale well with 250,000 CEs.

C: DMVPN requires routing protocol overlays which violate the requirement.

C. Fragment data packets: On slow WAN links, large data packets can delay small voice packets (serialization delay). Fragmentation ensures that voice packets are interleaved and not delayed behind large data frames (Link Fragmentation and Interleaving - LFI).

E. Prioritize voice packets: QoS mechanisms (LLQ, priority queuing) ensure that voice traffic is serviced first, reducing jitter and delay.

These are both critical QoS design principles for real-time application performance in constrained branch WAN scenarios, as outlined in CCDE v3.1.

Why other options are incorrect:

A: Increasing bandwidth may help but doesn’t address serialization or prioritization.

B: Memory upgrades do not directly improve voice quality.

D: Fiber upgrades do not address WAN-specific serialization or QoS.

PIM-SSM (Source-Specific Multicast) is optimized for multicast delivery directly via Shortest Path Tree (SPT) only.

SSM eliminates the need for shared trees (RPs), simplifies the control plane, and avoids rendezvous points altogether.

This design is highly scalable in multidomain and IPv6 environments, fully aligned with CCDE v3.1 best practices for modern multicast deployments.

Why other options are incorrect:

A: PIM-DM floods traffic initially, not SPT-based.

B: PIM-SM uses shared trees first and may switch to SPT later.

D: Bidir-PIM uses shared trees exclusively, not SPT.

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C (Significant effort and time): In a Waterfall model, changes introduced after the design phase require rework of multiple design documents, validations, and downstream impacts on implementation and testing. This leads to significant delays and resource consumption compared to more flexible models like Agile.

Other options explained:

A: Creativity is not the primary impact.

B: Rework is true but doesn’t fully capture the scope of additional effort.

D: Waterfall does not provide inherent flexibility to absorb late changes.

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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.

Cisco FabricPath is a Layer 2 multipath technology that blends traditional Layer 2 Ethernet with routing technologies to enable loop-free forwarding and scalability. Two critical mechanisms used to mitigate loops:

C. RPF (Reverse Path Forwarding) Check: FabricPath applies a reverse path forwarding check, similar to multicast, to verify the source of a frame and discard duplicates arriving on unexpected paths.

D. TTL Header: FabricPath adds a Time-To-Live (TTL) field to Layer 2 frames, which is not present in traditional Ethernet. This prevents indefinite circulation of frames by limiting their lifetime in the network—much like in IP.

These elements allow FabricPath to prevent broadcast storms and loops in multipath Layer 2 topologies, addressing legacy STP limitations with efficient loop-avoidance methods.

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B (Segment Routing): Allows traffic engineering and micro-segmentation across networks by steering traffic based on policies and labels.

D (Firewalls): Provide Layer 4-7 segmentation and security enforcement between segments.

Why other options are incorrect:

A: Policy-based routing influences forwarding, but is not a segmentation technology.

C: Data plane markings support QoS but do not create segmentation boundaries.

E: Filter lists are used in routing policy, not for full network segmentation.

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SNMPv3 is recommended as it supports authentication and encryption, protecting SNMP traffic even across service provider MPLS VPN backbones.

Healthcare environments require strong privacy and compliance (e.g., HIPAA), making SNMPv3 the correct protocol.

Why other options are incorrect:

B & C: Syslog is unrelated to SNMP traps.

D: SNMPv2 lacks security (unencrypted community strings).

E: SSH secures CLI access but not SNMP.

A picture containing table Description automatically generated

IPv4:

Host Registration - IGMP

Router Registration - PIM-DM, PIM-SM, SSM, BIDIR

Inter-Domain Source Discovery - MSDP

IPv6:

Host Registration - MLD

Router Registration - PIM-SM, SSM, BIDIR

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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B (Encrypt data when it is at rest and in motion): In hybrid cloud deployments, encryption is one of the most critical mechanisms to protect sensitive enterprise data both during storage (at rest) and while being transmitted (in motion). This ensures confidentiality and integrity across both private and public cloud environments.

Other options explained:

A: Using standard protocols is a general best practice but insufficient without encryption.

C: Communication of risks is part of compliance but does not enforce technical security.

D: Using standard protocols without encryption exposes data to risks.

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In this case, the bank seeks a solution that addresses scalability, manageability, application visibility, security (encryption and segmentation), and operational simplicity while aiming to reduce capital expenses. All these characteristics point directly to an SD-WAN architecture.

A non-managed (self-hosted) SD-WAN deployment:

Supports Zero Touch Provisioning (ZTP), reducing deployment time and operational burden.

Provides application-level visibility and intelligent path control.

Enables strong segmentation and end-to-end encryption via templates and policy engines.

Helps reduce CAPEX through the use of lower-cost broadband and centralized management.

While a “managed SD-WAN” solution (Option C) might be suitable in some cases, it typically involves higher OPEX. The question emphasizes CAPEX reduction, favoring an in-house SD-WAN solution.

This approach aligns with CCDE v3.1's “Scenario-based Design Strategy Guidance” and “Technology Comparisons and Use Cases” topics that emphasize selecting technologies aligned to business objectives and architectural scalability.

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C (QoS policy propagation with BGP - QPPB):Allows QoS policies to be dynamically applied based on BGP routing information, integrating policy control into routing decisions.

D (Remote black-holing trigger):Enables dynamic mitigation of attacks (e.g., DDoS) by injecting blackhole routes through BGP to selectively drop malicious traffic upstream.

Other options explained:

A/B/E: Static policy mechanisms that lack dynamic flexibility and responsiveness in modern service provider designs.

SNMPv1 and SNMPv2c use plaintext community strings and lack built-in encryption or authentication, making them vulnerable to various attacks, including spoofing and message tampering. SNMPv3 addresses these weaknesses by introducing:

Authentication (to prevent impersonation or "masquerade")

Encryption (privacy)

Message integrity

“Masquerade threats” involve an attacker pretending to be a trusted source, which SNMPv3 can prevent via cryptographic authentication mechanisms.

Although SNMPv3 does provide improved security features like integrity and privacy, it is not specifically designed to mitigate volumetric attacks like DDoS or dictionary brute-force. SNMPv3 does not inherently stop man-in-the-middle attacks unless secure key exchanges and trusted paths are fully enforced, which may require additional protocols.

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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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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+.

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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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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When an ACL is applied inbound on the Internet gateway interface facing the internal (trusted) network, the source IP address seen in the ACL will be the address after NAT translation has been applied to outbound traffic. This is called the inside global address:

Inside global = Public IP assigned by NAT to inside traffic for external use.

Inside local = Internal IP address prior to NAT.

Why other options are incorrect:

B, D: Outside addresses refer to external devices, not internal traffic.

C: Inside local is seen before NAT, not after.

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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.

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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EIGRP may be valid for initial deployment, but its scalability limitations — including proprietary nature, limited support over non-broadcast multipoint VPNs, and suboptimal convergence for large WAN overlays — make it most restrictive for future expansion.

BGP is typically the most scalable choice for large-scale VPN WAN deployments.

Why other options are incorrect:

B: IS-IS is not commonly deployed over Internet VPNs.

C: OSPF has better scalability than EIGRP for multi-area design but still limited over VPN overlays.

D: BGP is the preferred protocol for large-scale IPsec VPN WANs.

—

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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.

—

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.

Virtual Private LAN Service (VPLS) provides Layer 2 VPN connectivity over MPLS. Each Provider Edge (PE) device must learn and maintain MAC addresses per virtual instance.

PE Scalability is the primary concern: With 2000 VLANs, each PE participating in those instances must maintain a large forwarding table and handle associated control-plane activity.

MAC learning and aging, along with full-mesh label-switched paths (LSPs), place a heavy burden on CPU and memory.

Flooding (A) is expected but not the primary concern; it’s a symptom of scale.

The underlying transport (C) and VLAN ID limits (D) are important but not as critical in the context of PE resource scalability.

==========

D (Fate sharing):Fate sharing refers to a design where multiple dependent states fail together (i.e., when physical link fails, BGP session and its routes fail too).

Other options explained:

A: Fault isolation refers to containing failures, not dependent failure.

B: Resiliency is the ability to recover, not simultaneous failure.

C: Redundancy would prevent total loss if implemented.

D (L1/L2 for ABRs and L1 for internal routers):This hierarchical approach minimizes LSDB size inside areas (L1 routers only maintain intra-area routes) while L1/L2 routers handle inter-area route propagation, reducing neighbor adjacencies and improving scalability.

Other options explained:

A: Level 2 everywhere results in larger LSDBs across all routers.

B: Only L2 routers at ABRs would isolate L1 domains improperly.

C: Pure L1 design prevents inter-area reachability.

==========

B (RPVST+ — Rapid Per VLAN Spanning Tree Plus): Provides fast convergence while blocking redundant paths to prevent loops — fail closed behavior under failure scenarios.

C (MST — Multiple Spanning Tree): Provides loop prevention and isolates failures to specific instances (VLANs), maintaining fail closed protection.

Why other options are incorrect:

A: EIGRP is a routing protocol; does not operate at Layer 2 to provide fail-closed loop protection.

D: L2MP (Layer 2 Multipathing) allows multiple active links but requires additional loop prevention mechanisms.

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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.

Comprehensive and Detailed Explanation:

C: Before migrating to the cloud, organizations must conduct a thorough assessment of their current infrastructure. This includes evaluating applications, workloads, network topology, security posture, compliance requirements, and interdependencies. This step is essential for planning migration phases, identifying risks, and aligning architecture to business needs.

Other options:

A: SASE (Secure Access Service Edge) may be a future consideration but is not foundational to cloud readiness.

B: WAN optimization is important but comes after understanding infrastructure needs.

D: RPO/RTO calculations are part of disaster recovery, not initial cloud migration planning.

==========

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.

A (Address family translation):Since the requirement states that IPv4-only devices must be able to communicate with IPv6-only devices, anIPv4-to-IPv6 translation mechanismis necessary. NAT64, DNS64, or protocol translation (address family translation) allows devices on different IP families to communicate without requiring both sides to support both protocols.

Other options explained:

B (Dual stack): Allows both IPv4 and IPv6 to coexist on devices, but it does not solve the problem for IPv4-only or IPv6-only endpoints needing to interoperate.

C (Host-to-host tunneling): Requires both endpoints to support tunneling, which is not feasible for legacy devices.

D (6rd tunneling): Primarily enables rapid IPv6 deployment over IPv4 infrastructure, but does not enable interoperability between IPv4-only and IPv6-only devices.

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.

==========

The question describes a network that requires virtualization at both control and data plane levels using VLANs and VRFs. This architecture aligns with:

Path isolation (A): Achieved using VRFs and VLANs, ensuring traffic separation at Layer 2 and Layer 3 across the entire network.

Group virtualization (C): Refers to grouping users or resources (such as departments or tenants) into isolated segments that remain logically separated throughout the campus fabric.

Other options explained:

B (Session isolation): More aligned with application or session-layer security, not data/control plane virtualization.

D (Services virtualization): Typically related to virtualizing network services (firewalls, load balancers).

E (Edge isolation): Not a standard design term in CCDE.

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Reducing BGP keepalive and hold timers can help improve convergence but must be done carefully in provider-managed networks:

A: The service provider must agree to support modified timers on both PE and CE; otherwise, mismatched timer settings can break neighbor relationships.

C: The service provider may need to schedule configuration changes on PE routers to synchronize the timer adjustments and avoid service interruptions.

Why other options are incorrect:

B: Peer groups simplify policy application but do not impact BGP timers directly.

D: The number of routes affects convergence processing but not directly tied to timer adjustment.

E: The number of VRFs is a scalability consideration but unrelated to BGP timer negotiation.

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A (Posture assessment with remediation VLAN):Posture assessment checks endpoint compliance (such as AV definitions). Non-compliant devices are placed into a remediation VLAN where they can update before regaining normal network access.

Other options explained:

B: SGTs provide segmentation but are not posture-specific.

C: dACLs with SGTs handle policy enforcement, but posture control is required for AV compliance.

D: Quarantine VLAN isolates devices but doesn’t automate remediation.

C (Layer 2 switches unaffected):IPv6 operates at Layer 3, so pure Layer 2 switches forward frames without needing IPv6 awareness. As long as switches can transparently forward Ethernet frames, IPv6 functionality will be preserved, minimizing unnecessary hardware upgrades.

Other options explained:

A/B/D: These unnecessarily increase cost and complexity for basic Layer 2 functionality where IPv6 awareness is not mandatory.

B (Enable phone VPN authentication based on end-user username and password):When legacy devices don’t support certificate-based authentication, fallback to username/password provides a temporary workaround while maintaining PCI compliance, assuming strong credentials and secure tunnels are used.

Other options explained:

A: Immediate hardware replacement may not be feasible.

C: TLS 1.0 fallback violates PCI standards, which prohibit deprecated protocols.

D: Clear text authentication is non-compliant with PCI requirements.

Private cloud architecture provides:

On-demand provisioning and decoupling from hardware

Security controls under enterprise ownership

Strong isolation — comparable to an air-gapped model if fully controlled on-premises or in a dedicated hosted environment

While public or hybrid clouds offer flexibility, they cannot guarantee security parity with air-gapped systems unless significant additional controls are implemented. Private cloud supports containerized architectures and modern DevOps pipelines, while keeping the data plane within enterprise boundaries.

This aligns with CCDE’s cloud design principles — balancing modernization goals with strict compliance and cybersecurity mandates.

==========

Control plane hardening is a critical aspect of securing infrastructure devices. Recommended measures include:

A. Routing protocol authentication: Prevents unauthorized devices from injecting false routes by requiring secure key-based authentication (e.g., MD5 or SHA for OSPF/BGP).

B. SNMPv3: Provides secure management through authentication and encryption, preventing interception or modification of SNMP traffic.

C. Control Plane Policing (CoPP): Enforces rate limits and filtering for traffic directed to the device's CPU, protecting against DoS and control plane overloads.

Why other options are incorrect:

D. Redundant AAA servers support authentication resilience but are more about access control than direct control plane protection.

E. Warning banners are a legal and administrative best practice, not a technical control plane defense.

F. Enabling unused services is the opposite of best practices and increases the attack surface.

These control-plane protections are emphasized in CCDE v3.1 design guidance for resilient and secure infrastructure designs.

To support high-bandwidth, low-latency Layer 2 communication between DB Server 1 and DB Server 2, you must create a direct Layer 2 path between SW1 and SW2. Using REP (Resilient Ethernet Protocol) segments ensures loop-free Layer 2 operation without the drawbacks of STP convergence delays.

Option C is correct: Adding a third REP segment (Segment 3) directly between SW1 and SW2 isolates the traffic between the two DB servers and ensures deterministic behavior with fast convergence.

Option A (LACP with STP) introduces STP blocking and doesn’t align well with REP's control plane.

Option B and D: Overloading existing segments or splitting new links into existing REP segments does not offer the same direct path, bandwidth, or deterministic behavior.

==========

QoS queuing mechanisms such as LLQ (Low Latency Queuing), PQ (Priority Queuing), and CQ (Custom Queuing) operate at the interface level and are protocol-independent. Both IPv4 and IPv6 packets can be classified, queued, and scheduled using these mechanisms.

Why other options are incorrect:

B: Modern platforms support classification for IPv6 with hardware-based CEF.

C: Separate class-maps are typically required for IPv4 and IPv6.

D: The same queuing/congestion mechanisms apply to both IPv4 and IPv6.

—

PBR overrides the normal routing table behavior, potentially leading to microloops during reconvergence because forwarding decisions are based on policies rather than updated routing tables.

During fast topology changes, PBR decisions may not adapt as quickly as dynamic routing protocols, causing brief routing inconsistencies.

Why other options are incorrect:

A: PBR can add complexity but does not inherently limit scalability.

C/D: PBR does not directly affect convergence speed but can introduce inconsistency.

A (Design expecting outages and attacks):In WAN design, resiliency requires assuming that failures and attacks will occur. This drives the use of redundancy, diverse paths, and proactive failure mitigation techniques.

Other options explained:

B/C/D: While important, these focus on operational efficiency rather than core resiliency principles.

B (Minimize operational costs): A common business goal to reduce long-term operating expenses.

E (Reduce complexity): Simplifying designs reduces operational overhead, risk, and failure domains.

Why other options are incorrect:

A: Resiliency is a design goal, but not a business objective itself.

C: Endpoint posture is a technical security feature.

D: Faster obsolescence contradicts business optimization.

Fate-sharing describes a situation where two or more services or components are tied together such that failure in one leads to failure in others. In resilient design, the goal is often to eliminate fate-sharing by decoupling dependencies.

A: A single point of failure (like a shared power supply or converged service path) that brings down multiple components exemplifies fate-sharing.

B is incorrect because fate-sharing is a risk, not a protective measure.

C and D refer to device behavior (stateful inspection, transport layer behavior) rather than architectural dependency.

==========

A (VXLAN offers native loop avoidance): VXLAN uses Layer 3 underlay with encapsulation, inherently avoiding Layer 2 loops common in traditional Layer 2 fabrics.

Why other options are incorrect:

B: Storm control mitigates broadcast storms but doesn't prevent loops.

C: vPC+ helps but doesn’t replace VXLAN's loop-free architecture.

D: BPDU Guard helps protect edge ports, but loop prevention in VXLAN is primarily handled by its Layer 3 foundation.

The performance degradation is caused by output queue drops on the 1 Gbps server port. Increasing the queue size allows more data to be buffered during transient congestion periods, preventing packet loss and retransmissions which significantly degrade iSCSI performance.

iSCSI is sensitive to packet loss due to its reliance on TCP.

Increasing the queue depth is a simple, cost-effective method to absorb bursts.

Changing to CIFS (A) is irrelevant since CIFS would suffer similar TCP congestion.

WRED (C) intentionally drops packets during congestion, which is undesirable here.

Enabling TCP Nagle (D) would likely introduce latency and reduce throughput for large data transfers.

—

Comprehensive and Detailed Explanation:

Central command and control refers to a unified, centralized security policy and management platform that integrates and coordinates all security components—regardless of physical location or form factor (virtual, physical, cloud). It streamlines operations, reduces overhead, and improves visibility and control.

D is correct because central control simplifies policy enforcement and visibility.

A (threat-centric protection) focuses more on response and defense rather than architecture.

B (integrated actionable intelligence) refers to threat feeds, not central management.

C (distributed enforcement) is an implementation strategy, not a management component.

==========

In this architecture:

A secure web proxy is introduced to inspect and filter all web (HTTP/HTTPS) traffic.

Remaining traffic (non-web) must pass through an NGFW with IPS capabilities.

Both the web proxy and NGFW reside between the collapsed distribution/core and internet edge.

To enforce that all web traffic is directed to the proxy appliance for inspection and non-web traffic follows its usual path to the NGFW:

A. Policy-Based Routing (PBR) on the Collapsed Core

This allows traffic classification based on destination port (e.g., TCP 80/443) and selectively reroutes web traffic to the proxy. Non-web traffic continues toward the NGFW. PBR is essential here because traditional routing (based only on destination IP) would not differentiate between traffic types.

D. Static Routing on the Appliance

The proxy appliance must return the traffic back toward the NGFW for final processing and internet egress. This is typically achieved using static routes on the proxy device, ensuring the return path sends packets back to the correct firewall interface for consistent inspection.

❌B. Policy-based routing on the internet edge: Not applicable here, as rerouting must occur closer to the source (collapsed core), before traffic reaches the internet edge.

❌C. Policy-based routing on firewalls: This adds unnecessary complexity. Firewalls should focus on enforcing security policies, not traffic redirection logic in this scenario.

This approach adheres to CCDE v3.1 best practices by separating policy enforcement functions and enabling scalable, deterministic traffic flow through layered security appliances.

To split an Ethernet domain and ensure isolation of configuration and topology changes, the key mechanism is separating the VLAN management domains. This is achieved through:

VTP (VLAN Trunking Protocol) domain separation

Each VTP domain controls its own set of VLAN information and will not propagate VLAN changes across domain boundaries. By assigning unique VTP domain names to each half of the network, administrators prevent unintended synchronization of VLANs between switches.

Other options:

B. VTP password: Adds security but does not separate domains.

C. STP type: All switches in the domain can run the same or different STP versions and still be part of the same Ethernet domain.

D. VLAN ID: These can overlap across domains; uniqueness is not required to split domains.

==========

B (Support availability):Defines hours of service and whether support is available 24/7 or during business hours.

E (Resolution time):Specifies the timeframe within which the service provider commits to resolve incidents.

Other options explained:

A: Cost and size are contractual, not SLA performance metrics.

C: Sustainability is long-term environmental or operational, not SLA-specific.

D: Reliability is often captured as uptime or availability but not as a discrete SLA support term.

C (Both modes use control packets):Regardless of whether echo packets are used, BFD asynchronous mode always relies on periodic transmission of control packets to verify session liveliness.

E (Echo mode uses separate packets):When echo is enabled, the echo packets are transmitted in addition to control packets, providing even faster failure detection by relying on data plane processing.

Other options explained:

A: Control and echo packets are never combined into a single packet.

B: Both modes always use control packets; echo packets are optional.

D: BFD echo packets are locally looped, not reflected back from the remote device.

While the Agile Manifesto itself is not a network-specific construct, its values are relevant to business-driven network design approaches outlined in CCDE v3.1—especially when designing flexible and adaptive systems. One of the core values of Agile is:

→ “Individuals and interactions over processes and tools”

This emphasizes that communication and collaboration among people are more crucial than relying solely on formal tools or rigid processes. For network architects and designers, this translates into focusing on team collaboration and business alignment during iterative design cycles.

Incorrect Options:

A, B, and D are all reversed versions of Agile’s actual values; they incorrectly prioritize the right-hand side.

==========

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 & 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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A (EoMPLS): Ethernet over MPLS can operate at Layer 2, and MACsec can encrypt traffic before entering the MPLS core.

E (KVPLS): Supports MACsec encryption for Layer 2 DCI services over VPLS solutions.

Why other options are incorrect:

B: MPLS L3 VPN operates at Layer 3, not suitable for MACsec (L2 encryption).

C: DMVPN uses IPsec, not MACsec.

D: GET VPN uses IPsec for L3 traffic encryption.

—

Table Description automatically generated

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.

TOGAF (The Open Group Architecture Framework) provides a full enterprise architecture methodology including:

Business requirements gathering

Gap analysis

Architecture modeling

Comprehensive design documentation

TOGAF is widely referenced in CCDE v3.1 for high-level architecture development.

Why other options are incorrect:

B (ITIL): Focuses on service management, not architecture design.

C (FCAPS): Defines network management functional areas.

D (COBIT): Focuses on governance and compliance, not design frameworks.

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D (High latency):In three-tier architectures, east-west traffic between different pods (access domains) must traverse additional layers (distribution and core), introducing extra hops and thus adding latency. This inefficiency is one reason why spine-leaf architectures are favored for modern data centers.

Other options explained:

A: Bandwidth is less of a concern with high-speed core links.

B: Security is not directly affected by east-west traversal in this architecture.

C: Scalability is limited, but the primary issue for east-west traffic is latency.

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.

==========

Comprehensive and Detailed Explanation:

D: The most effective solution is to have Site-X advertise a more specific (longer) prefix (e.g., 100.75.10.0/24), which allows external BGP routers to prefer Site-X over Site-Y. This ensures traffic destined for Site-X flows directly to it, preserving symmetry. Additionally, control plane coordination between R1 and R2 ensures proper routing consistency and minimizes the risk of loops or misdirection.

Other options:

A: Using BGP MED works within the same AS; it is often ignored by external ISPs.

B: Replicating firewall behavior does not address the routing issue.

C: DNS manipulation is a workaround—not a scalable or robust design solution.

This solution is consistent with BGP best practices and CCDE v3.1 guidance on traffic engineering and policy-based routing.

C (Synchronous replication across data centers):Synchronous replication ensures zero or near-zero data loss (very low RPO), as data is written simultaneously to both sites. For an RPO of under 10 seconds, synchronous replication is mandatory.

Other options explained:

A: Asynchronous replication may result in higher RPO.

B/D: Single site designs introduce single points of failure for business continuity.

Cisco SD-WAN Cloud OnRamp SaaS optimizes cloud application performance by dynamically measuring SaaS application paths from multiple branch edges toward the Microsoft 365 cloud.

It automatically selects the best-performing path, continuously monitors SLA metrics (latency, loss, jitter), and dynamically reroutes based on real-time performance.

This directly addresses SaaS resiliency across multiple ISPs with minimal manual intervention and is aligned with CCDE v3.1 SD-WAN design methodologies for SaaS optimization.

Why other options are incorrect:

A: Cloud OnRamp gateway is for IaaS optimization (AWS, Azure), not SaaS.

B: Cloud OnRamp SWG (Secure Web Gateway) is for internet-bound security inspection, not SaaS path optimization.

C: "Cloud OnRamp" alone is too general; SaaS is the specific solution for this SaaS use case.

FCoE (Fibre Channel over Ethernet) requires a lossless Ethernet transport, typically achieved using Data Center Bridging (DCB) features such as Priority Flow Control (PFC). Only technologies that can preserve Ethernet frames end-to-end and support lossless characteristics can properly carry FCoE:

A. DWDM (Dense Wavelength Division Multiplexing): Operates at the physical layer and is transparent to Ethernet, preserving frame integrity and lossless characteristics across long distances.

B. EoMPLS (Ethernet over MPLS): Carries Ethernet frames directly over MPLS and can be engineered to support low-loss, low-latency transport appropriate for FCoE.

Why other options are incorrect:

C. SONET/SDH encapsulates Ethernet but is not suitable for FCoE due to differences in timing and buffering.

D. Multichassis EtherChannel over pseudowire may introduce additional control plane complexity and loss characteristics.

E. VPLS introduces MAC learning, flooding, and buffering behaviors that can cause frame loss, which is not compatible with FCoE requirements.

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A (QoE estimation): In SDN-based designs, particularly for multimedia traffic (voice, video, streaming), Quality of Experience (QoE) estimation is crucial to ensure end-user satisfaction. SDN can dynamically allocate resources based on real-time measurements of packet loss, jitter, delay, and other QoE indicators to maintain service quality.

Other options explained:

B: Security is always important but not unique to multimedia design.

C: Traffic patterns are part of capacity planning but secondary to QoE for multimedia.

D: Flow forwarding is handled by the SDN controller but does not directly address multimedia quality.

—

B (Kubernetes):Kubernetes is designed for container orchestration with full state-awareness, handling deployment, scaling, failover, and service discovery. It continuously monitors and maintains the desired state across distributed microservice deployments.

Other options explained:

A: Puppet handles configuration management, not container orchestration.

C: Ansible provides automation but lacks native orchestration state tracking.

D: Terraform handles infrastructure provisioning, not runtime service orchestration.

In addition to business requirements, network architects must also account for non-business constraints such as legal, regulatory, and industry compliance. These may include standards like GDPR, HIPAA, PCI-DSS, or country-specific data sovereignty and retention laws.

Compliance is not typically driven by direct business value but by external mandates that influence how the network must be designed, implemented, and operated. Ignoring compliance requirements can result in significant legal or financial penalties and is therefore a core component of any responsible network design.

Other options such as:

A. Location — may impact design (e.g., latency, availability), but it is often categorized as a technical or logistical consideration.

B. Cost — is a business constraint.

C. Time — is considered a project or delivery constraint, also typically business-driven.

B (Micro loops):OSPF Loop-Free Alternates (LFA) pre-calculate backup next-hops to reduce transient micro loops during the convergence process when primary routes fail.

Other options explained:

A: DTP relates to trunk negotiation, not loop prevention.

C: STP handles Layer 2 loops.

D: REP is a Cisco Layer 2 redundancy protocol, unrelated to OSPF loop prevention.

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.

A (BPDU Guard on access ports): Prevents accidental connection of switches or bridging devices on access ports, which could cause unexpected topology changes or loops.

C (Root Guard on aggregation switch downlinks): Ensures access switches cannot send superior BPDUs to challenge aggregation switch root status, maintaining predictable STP root placement.

Why other options are incorrect:

B: Aggregation downlinks are not normally configured with BPDU Guard (since they expect BPDUs from access switches).

D: Root guard on access ports is unnecessary as those ports should not participate in STP.

E: Edge port (Rapid STP concept) is good for faster convergence but doesn't address stability.

F: STP root and backup root election is important but not a specific STP feature — this is a design decision, not a stability feature.