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

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.

Application performance depends on the end-to-end delay experienced by the traffic, which includes:

Queuing delay at each device.

Serialization delay based on link speed and packet size.

Propagation delay.

For the application to meet its performance SLA, the total of all delays (queuing + serialization + propagation) must remain within the application ' s maximum tolerable delay budget. This is critical for delay-sensitive applications such as voice or real-time video.

This directly aligns with CCDE v3.1 business-driven design, where application requirements dictate network performance guarantees.

Why other options are incorrect:

A: Focusing on individual devices ignores cumulative delay.

B: Uniform queuing delay isn’t practical or necessary.

C: Default queue sizes are not always suitable for real-time applications.

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C (NFV - Network Functions Virtualization):ETSI NFV framework allows virtualizing network functions (firewalls, load balancers, etc.) on standard hardware, promoting flexibility, cost reduction, and hardware independence.

Other options explained:

A: NPIV relates to Fibre Channel storage, not network virtualization.

B: NFVIS is Cisco ' s NFV infrastructure software, not the ETSI standard itself.

D: VNF refers to individual virtualized functions, not the framework.

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.

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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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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DUMPS (Designated Unified Multiprotocol Redistribution Strategy) using single-point redistribution with route tagging ensures scalable, loop-free redistribution.

Route tags prevent redistributed routes from being re-advertised into the originating protocol, avoiding routing loops even with multiple paths.

Single-point redistribution simplifies operational complexity compared to multipoint redistribution.

Why other options are incorrect:

A, B, D: ACLs are not scalable for filtering redistributed routes in large networks. Tags provide better control.