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

MLD (Multicast Listener Discovery) snooping for IPv6 operates similarly to IGMP snooping in IPv4. It tracks listener reports to restrict multicast flooding within a Layer 2 domain.

C: Querier elections are triggered when a querier becomes unreachable or its IP address changes.

D: The querier with the lowest IPv6 address is elected as the active querier, which manages report/query communication.

Other options:

A: QoS is not automatically enabled with MLD snooping.

B: MLD querier functionality operates per VLAN—not per group—so only one querier is elected per VLAN.

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Table Description automatically generated with medium confidence

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.

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C: MPLS TE (Traffic Engineering) is designed to optimize IP traffic flow by considering bandwidth constraints, delay sensitivity, and administrative policy. It enables operators to steer traffic based on defined metrics rather than pure shortest-path IGP routes.

Other options:

A: MPLS TE can coexist with LDP and still rely on IGP for link-state info; it does not replace LDP.

B: MPLS TE by itself doesn’t provide protection; it requires Fast Reroute (FRR) mechanisms like link/node protection extensions.

D: MPLS TE is independent of VPN topology; it can operate without requiring a full-mesh of Layer 3 VPNs.

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BFD (Bidirectional Forwarding Detection) provides sub-second failure detection at the control plane level, making it the fastest convergence mechanism for Layer 3 routing protocols.

Fiber Ethernet typically offers higher reliability and lower latency than copper.

When combined, Fiber with BFD provides the most robust and quickest convergence for unidirectional failures in a routed data center environment.

Why other options are incorrect:

A & B: Copper adds more physical susceptibility to errors.

B & D: UDLD is a Layer 2 unidirectional detection mechanism, not optimized for Layer 3 convergence.

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B (EAP - Extensible Authentication Protocol):EAP is commonly used for 802.1X port-based authentication, allowing identity-based control for users on the network. This enables policy enforcement, identity-based segmentation (micro/macro segmentation), and leverages existing domain credentials via backend integration.

Other options explained:

A: LDAP is backend directory, not an authentication protocol for access ports.

C: TACACS+ is used primarily for administrative access.

D: RADIUS transports the EAP exchange but is not the authentication protocol itself.

B (Added redundancy): Redundancy ensures alternate paths or systems are available if a failure occurs, which is the primary design principle behind resiliency. Redundancy directly contributes to higher network availability and fault tolerance.

Why other options are incorrect:

A: Load-balancing optimizes performance but doesn’t inherently improve resiliency.

C: Confidentiality addresses security, not resiliency.

D: Reliability is an outcome, not a design principle itself.

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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.

FCAPS stands for Fault, Configuration, Accounting, Performance, and Security.

D (Authentication) is not a management category within the FCAPS framework.

Authentication is part of security functions but not a standalone FCAPS category.

Why other options are correct FCAPS components:

A: Configuration management

B: Security management

C: Performance management

E: Fault management

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In the Cisco three-layer hierarchical design model (Access, Distribution, Core), the access layer is primarily responsible for:

Providing user/device connectivity.

Enforcing policy boundaries.

Performing QoS classification and marking at ingress.

The access layer is the optimal point to classify and mark traffic for QoS because:

It is the first point of entry into the network for end-user devices.

Markings can then be trusted by upstream devices (distribution and core).

This minimizes trust boundaries throughout the network and ensures consistent policy enforcement.

This design principle ensures end-to-end QoS consistency, a key objective emphasized in CCDE v3.1 for scalable and maintainable enterprise designs.

Why other options are incorrect:

A (Fault isolation): Typically handled at distribution/core layers.

C (Reliability): A general network-wide requirement, not specific to access.

D (Fast transport): Primarily a core layer function.

E (Redundancy and load balancing): Managed primarily at distribution and core layers.