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

D (SAML2.0):SAML2.0 is widely used for federated identity management in enterprise environments, supporting Single Sign-On (SSO) across multiple applications and domains.

Other options explained:

A: OAuth2 is primarily for authorization, not identity federation.

B: OpenID Connect extends OAuth2 for authentication but is more common for consumer web apps than enterprise SSO.

C: OpenID is older and largely replaced by OpenID Connect.

B (Transport Mode in IPsec Phase II):When GRE is running over IPsec,IPsec Transport Modeis often preferred. In Transport Mode, only the payload (GRE encapsulated packet) is encrypted and authenticated, while the original IP header remains untouched. This eliminates redundant IP headers, avoiding duplicate addressing and reducing overhead — optimizing bandwidth efficiency across the Internet VPN.

GRE provides the tunneling function, while IPsec in Transport Mode secures the GRE-encapsulated traffic. Transport Mode is negotiated duringIPsec Phase II (Quick Mode), where actual data protection parameters are established.

Other options explained:

A:Phase I is for establishing secure channels, not for data encapsulation.

C:Tunnel Mode would encapsulate the entire packet (including GRE header), adding unnecessary additional IP headers in this GRE over IPsec design.

D:Tunnel Mode does not apply at Phase I — Phase I is only for IKE negotiation.

B (Separation of infrastructure and policy):SD-WAN decouples policy control from the underlying transport.

C (Simpler policy-based forwarding):Centralized controllers dynamically steer traffic according to application policies with less complexity than traditional QoS in MPLS.

Other options explained:

A: FEC (Forward Error Correction) is typically not used in standard SD-WAN implementations.

D: SD-WAN does not unify WAN backbones; it abstracts multiple underlays.

E: Both MPLS and SD-WAN have failure management, but SD-WAN focuses more on dynamic path control than simply backup links.

ChatGPT said:🟦 QUESTION NO: 391

[Main Topic: Scenario-Based Design Strategy Guidance]

Feature-rich and attributed networks are used to model complex systems where nodes and links can represent various relationships and characteristics. Which two alternative network models can be used to model interactions over time or by specific relationships?

A. heterogeneous network

B. information network

C. location-aware network

D. multilayer network

E. probabilistic network

F. temporal network

Answer: D, F

🔍Comprehensive Explanation:

D. Multilayer Network:This model captures different types of relationships or interactions by separating them into layers. Each layer can represent a specific attribute (e.g., organizational structure, communication paths, or access levels), enabling a more granular view of network behaviors or dependencies.

F. Temporal Network:A temporal network models interactions over time by including timestamps or time intervals for each interaction or link. It’s well-suited for analyzing dynamic behaviors such as traffic flow, communication logs, or transaction timelines.

Other options:

❌A. Heterogeneous Network: Refers to networks composed of different technologies or platforms, not necessarily different types of attributes or timelines.

❌B. Information Network: This is a general term and does not specifically define a structured modeling approach for attributes or time.

❌C. Location-Aware Network: Involves geolocation or spatial data but does not inherently model time or multi-attribute structures.

❌E. Probabilistic Network: Uses probability distributions to model uncertain events, not ideal for modeling time or attributes.

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🟦 QUESTION NO: 392

[Main Topic: Business-Driven Design Approaches]

A company is assessing their technology landscape before moving to the cloud. They observe that over 5000 servers have less than 50% capacity utilization. What cloud architecture model best supports optimizing resource utilization?

A. homogenous cloud

B. heterogenous cloud

C. hybrid-private cloud

D. public cloud

Answer: D

🔍Comprehensive Explanation:

D. Public Cloud:Public cloud services provide elastic and scalable infrastructure. For workloads with low or variable utilization, public cloud offers pay-as-you-go models that significantly reduce the overhead of underutilized on-prem hardware. This is ideal for shifting capital expenditure (CAPEX) to operational expenditure (OPEX), achieving better cost efficiency.

Other options:

❌A. Homogenous Cloud: Not a standard term; it might imply uniform hardware/software environments, but it doesn’t address utilization.

❌B. Heterogenous Cloud: Typically used to describe mixed environments but doesn’t directly offer utilization optimization.

❌C. Hybrid-Private Cloud: Offers flexibility and data control but still often involves maintaining some level of underused on-prem resources unless carefully managed.

Bit Indexed Explicit Replication (BIER) eliminates the need for traditional multicast signaling protocols such as PIM.

BIER uses IGP extensions (e.g., OSPF or ISIS) to advertise BIER forwarding state.

The BIER header contains a bit-string indicating directly which receivers should receive the multicast packet, removing the need to build trees via signaling.

This design is emphasized in CCDE v3.1 as a significant advancement for efficient, scalable multicast in large modern service provider and enterprise networks.

Why other options are incorrect:

A, B, D: These options are invalid or fictitious terms in multicast protocol standards.

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

Agile practices and DevOps principles are foundational to infrastructure modernization. Agile enables iterative development, collaboration, and responsiveness to change, while DevOps unifies development and operations, fostering automation, monitoring, and continuous delivery. These elements improve not just technical efficiency but also cultural alignment across teams, boosting productivity and adaptability.

Infrastructure-as-code (Option B) supports automation but is an enabler—not a cultural component by itself. Controlled and dedicated infrastructure reflects traditional IT models that lack agility and flexibility.

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During massive BGP update events (such as after a topology change), a route reflector may struggle processing both BGP updates and the resulting TCP acknowledgments required for reliable BGP session communication.

Increasing the hold queue size allows the router to buffer more packets waiting for processing (including TCP acknowledgments), helping the router handle bursts of BGP updates without dropping TCP segments or tearing down sessions.

This queue tuning is a well-known scalability optimization in CCDE v3.1 when designing route reflector clusters handling large-scale control plane updates.

Why other options are incorrect:

B & C: Adjusting buffer sizes does not directly address TCP acknowledgment backlog.

D: Keepalive timers control session liveliness, not update processing.

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The distribution layer serves as the boundary between the access and core layers in the three-tier hierarchical design. It plays a crucial role in providing policy enforcement, control, and boundary functions, including:

QoS classification and marking (C): The distribution layer serves as the boundary for Quality of Service policies. It marks and classifies traffic as it moves from access to core layers, ensuring proper QoS treatment in the core.

Redundancy and load balancing (E): The distribution layer provides link redundancy (e.g., dual-homing access layer switches) and performs load balancing to optimize path selection toward the core.

Other options explained:

A (Fast transport): Typically associated with the core layer, which focuses on high-speed forwarding.

B (Reliability): While reliability is a network-wide goal, it’s not a primary function of the distribution layer specifically.

D (Fault isolation): While partial fault containment occurs, primary fault isolation happens at the access layer.

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A (Additional MPLS provider):True path diversity includes provider diversity to eliminate the possibility of shared failures within a single provider’s infrastructure. Multiple providers minimize correlated failures, increasing WAN availability.

Other options explained:

B: Out-of-band management improves operational access but doesn't address WAN availability.

C: Dual-homing branches is valuable but not directly related to the data center’s WAN failure condition.

D: Hardware redundancy improves local device availability but doesn't mitigate WAN failures.

DTLS (Datagram Transport Layer Security) is the most optimized overlay protocol for SDWAN deployments over public internet, especially when NAT traversal is required.

It combines security similar to TLS while using UDP, which handles packet loss, jitter, and reordering better than TCP-based TLS.

DTLS is natively supported in most SDWAN solutions for encrypted transport across NAT environments without complex configurations.

It allows optimal performance on unreliable or high-latency networks while maintaining strong security standards.

Why other options are incorrect:

A (TLS): Uses TCP, less suited for networks with packet loss or reordering.

C (IPsec): Requires additional NAT traversal mechanisms like NAT-T and may not handle unreliable underlay as effectively as DTLS.

D (GRE): Tunneling protocol without native encryption.

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