Pass the Cisco CCDE v3.0 400-007 Questions and answers with ExamsMirror

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.

B (Use only secure protocols): Management and administrative access to Internet edge routers must use secure protocols (SSH, SNMPv3, HTTPS) to prevent interception or unauthorized access.

E (Restrict administrative access): Limiting administrative access via interface ACLs and clear login banners ensures that only authorized personnel can access the system, satisfying compliance and security requirements.

Other options explained:

A: Filtering infrastructure IP space is good hygiene but not directly related to compliance.

C: Logging is valuable for operations and incident response but not a compliance control by itself.

D: EBGP advertisements relate to routing policy, not compliance regulation.

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.

A (Enhance TCP performance):Path MTU Discovery allows TCP to dynamically learn the maximum transmission unit (MTU) along the path and avoid fragmentation. This reduces retransmissions, maximizes throughput, and improves efficiency for TCP-based applications such as BGP.

Other options explained:

B/C: PMTUD does not affect convergence times.

D: Loop prevention is unrelated to MTU discovery.

Just-in-time (JIT) manufacturing relies on precision timing and real-time data exchanges between production systems and external suppliers. Network latency can directly impact the efficiency and viability of such a system. For this reason, the architect must prioritize a network design that ensures minimal delay and rapid delivery of application and sensor data.

According to CCDE v3.1 design principles, when latency is tied directly to business outcomes (e.g., manufacturing workflow dependencies), the network must be designed with a focus on:

End-to-end low-latency infrastructure

Predictable jitter and delay control

Application prioritization mechanisms (QoS)

High availability and redundancy

This allows the manufacturer to optimize production throughput while reducing delays caused by communication lag with external component providers.

Why other options are incorrect:

A. Automation helps with operational efficiency, but it does not directly ensure low-latency communication.

B. Zero Trust is a security model, not latency-related.

D. Modularity is about design structure, not latency performance.

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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.

SD-WAN design principles:

C: Centralized policy, simplified management, and dynamic path selection improve operational efficiency, directly resulting in cost savings.

D: SD-WAN provides centralized orchestration, automation, and zero-touch provisioning, simplifying deployment and scaling.

Why other options are incorrect:

A: SD-WAN improves performance with features like dynamic path selection but cannot inherently prevent slow underlay performance.

B: Many SD-WAN solutions logically separate control and data planes, but not all strictly follow full separation like traditional SDN.

E: SD-WAN is typically hardware-agnostic but does not depend on specialized switching hardware.

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.

A (DAI - Dynamic ARP Inspection): Prevents ARP spoofing attacks on the data plane.

B (IP Source Guard): Prevents IP address spoofing by verifying IP/MAC bindings against DHCP snooping tables.

Both are directly applied to securing the data plane (traffic forwarding layer).

Why other options are incorrect:

C (BEEP): A transport protocol, not a data plane security feature.

D (CPPr): Protects the control plane, not data plane.

E (MPP): Protects management plane, not data plane.

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To achieve subsecond convergence in IS-IS or OSPF networks and quickly detect both:

Link-layer failures (e.g., interface flaps)

Control-plane adjacency loss

The best solution is:

C. BFD (Bidirectional Forwarding Detection): A lightweight protocol that enables subsecond failure detection, independent of the IGP timers, by establishing fast detection sessions over forwarding paths.

This is widely deployed in high-performance networks to accelerate convergence without compromising routing stability.

Why other options fall short:

A. Debounce timers delay interface-down events (not suitable when fast detection is required).

B. Fast hellos affect hello interval but are still slower and CPU-intensive.

D. LSP fast flood improves LSP propagation but doesn’t address failure detection speed.

This solution is central to CCDE “Protocol Design Implications” where rapid failure detection and recovery drive the convergence architecture.

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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.

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Table Description automatically generated

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.

B (IP Source Guard):IP Source Guard prevents IP address spoofing at Layer 2 by binding IP-to-MAC addresses and filtering unauthorized source IPs. It operates independently of encryption, so it has no impact on encryption performance.

Other options explained:

A: MACsec adds encryption and has performance implications.

C: DHCP snooping with DAI focuses on ARP spoofing, not IP address antispoofing specifically.

D: IPsec handles encryption, which directly impacts performance.

UplinkFast is an STP optimization feature designed primarily for access layer switches to reduce convergence time when a direct link failure occurs. When a primary uplink fails, UplinkFast immediately activates a backup uplink port without waiting for traditional STP convergence.

It is most effective on access layer switches where redundant uplinks to distribution switches exist.

On distribution switches, it may also be useful if they have multiple uplinks toward the core.

UplinkFast is not recommended for core switches as these typically don’t have redundant uplinks toward lower-tier devices.

It is not designed to resolve interoperability issues between different STP versions or to adjust hello timers.

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