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

In data center migration scenarios, when legacy and VXLAN EVPN networks are connected for host mobility, a critical step is to ensure a seamless Layer 3 gateway handoff. This is typically achieved using VRRP (or HSRP) where both the old and new gateways share the same virtual IP.

The final step involves:

Increasing the VRRP priority on the new VXLAN-enabled infrastructure to make it the active default gateway.

Ensuring that hosts retain their original default gateway (no reconfiguration required).

Only after the new gateway is active, the legacy SVIs can be gracefully shut down.

This method ensures no packet loss or disruption to host connectivity during or after migration.

It aligns with CCDE v3.1 under the “Network Architecture Principles” domain, particularly for data center transformation, operational consistency, and seamless L2–L3 handoff design patterns.

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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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.

B (Confidentiality):Protects data from unauthorized access or disclosure.

E (Integrity):Ensures data remains accurate and unaltered.

F (Availability):Ensures that data and systems are accessible when needed.

Other options explained:

A: Cryptography is a tool used to achieve confidentiality, integrity, or authentication, but it's not part of the CIA triad itself.

C/D: Authorization and identification are security processes, but not part of the core CIA triad.

D (Deploy SD-WAN edge routers in data center, then controllers, then branches):This allows the SD-WAN fabric to be built and stabilized centrally first, then controllers are brought online for policy orchestration, and finally, branch migrations happen gradually without impacting existing traffic paths.

Other options explained:

A/B/C: These approaches risk service disruption or poor controller orchestration readiness during branch migrations.

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 (IPFIX telemetry data):IPFIX provides detailed flow-level visibility, enabling identification of traffic patterns, data flows, and destinations. This data is critical for understanding current traffic behavior to identify governance gaps and improve policy compliance.

Other options explained:

A: Secure tunnels protect traffic but do not identify governance gaps.

C: Firewalls provide limited flow visibility compared to telemetry.

D: Workload policies enforce security but do not aid initial visibility analysis.

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.

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B (Northbound APIs):Northbound APIs allow applications to communicate with the SDN controller to express service requests and provide policy intent. The controller translates these into instructions for the underlying infrastructure.

Other options explained:

A: Southbound APIs connect controllers to forwarding devices.

C: Orchestration coordinates workflows across domains but doesn’t directly connect applications to controllers.

D: The SDN controller receives the northbound API calls but is not the API itself.

The goal is to prevent AS 111 from being used as a transit AS.

The most effective method is to use an AS path access list to filter outbound BGP advertisements, allowing only prefixes originated from AS 111 (AS path contains only AS 111).

This ensures AS 111 only advertises its own prefixes and does not forward third-party prefixes between providers.

Why other options are incorrect:

A: AS-set is used for aggregation, not for transit prevention.

B: Local preference controls outbound path selection, not advertisement or transit.

D: Prefix list on inbound filters received prefixes, but does not prevent transit.

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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.

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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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D (EoMPLS - Ethernet over MPLS):EoMPLS allows Layer 2 extension across MPLS without IP addressing or routing changes, preserving VLANs and broadcast domains — ideal for extending CCTV networks transparently.

Other options explained:

A: GRE encapsulates Layer 3, requiring IP configurations.

B: L2TPv3 is possible but not common over MPLS SP networks.

C: VXLAN is more suited for data center overlays, not WAN/MPLS integration.