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

D (GRE Key and Sequence Number extensions):The GRE Key field provides session identification for distinguishing between multiple GRE tunnels. The Sequence Number extension allows endpoints to track packet ordering and detect lost or out-of-order packets, enhancing reliability at the tunnel level if required.

Other options explained:

A: Protocol Type identifies payload type; Checksum detects errors but doesn ' t provide sequencing.

B: GRE Version and Reserved0 fields are not used for session or sequencing.

C: GRE does support optional extensions, contrary to this statement.

SNMPv1 and SNMPv2c use plaintext community strings and lack built-in encryption or authentication, making them vulnerable to various attacks, including spoofing and message tampering. SNMPv3 addresses these weaknesses by introducing:

Authentication (to prevent impersonation or " masquerade " )

Encryption (privacy)

Message integrity

“Masquerade threats” involve an attacker pretending to be a trusted source, which SNMPv3 can prevent via cryptographic authentication mechanisms.

Although SNMPv3 does provide improved security features like integrity and privacy, it is not specifically designed to mitigate volumetric attacks like DDoS or dictionary brute-force. SNMPv3 does not inherently stop man-in-the-middle attacks unless secure key exchanges and trusted paths are fully enforced, which may require additional protocols.

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D (Lifecycle model):The lifecycle model aligns directly with traditional project management (such as Waterfall). It follows a sequential, phase-driven process: requirement gathering, design, implementation, testing, and maintenance. Each phase must be completed before moving to the next, with defined milestones and documentation.

Other options explained:

A: " Static model " is not a standard recognized development model.

B: Agile is iterative and adaptive, opposite of traditional models.

C: Evolutionary delivery is more incremental, not fully aligned with traditional models.

C (Significant effort and time): In a Waterfall model, changes introduced after the design phase require rework of multiple design documents, validations, and downstream impacts on implementation and testing. This leads to significant delays and resource consumption compared to more flexible models like Agile.

Other options explained:

A: Creativity is not the primary impact.

B: Rework is true but doesn’t fully capture the scope of additional effort.

D: Waterfall does not provide inherent flexibility to absorb late changes.

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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.