Cisco Updated 400-007 Exam Questions and Answers by jennifer

B (Transport Mode in IPsec Phase II):When GRE is running over IPsec,IPsec Transport Modeis often preferred. In Transport Mode, only the payload (GRE encapsulated packet) is encrypted and authenticated, while the original IP header remains untouched. This eliminates redundant IP headers, avoiding duplicate addressing and reducing overhead — optimizing bandwidth efficiency across the Internet VPN.

GRE provides the tunneling function, while IPsec in Transport Mode secures the GRE-encapsulated traffic. Transport Mode is negotiated duringIPsec Phase II (Quick Mode), where actual data protection parameters are established.

Other options explained:

A:Phase I is for establishing secure channels, not for data encapsulation.

C:Tunnel Mode would encapsulate the entire packet (including GRE header), adding unnecessary additional IP headers in this GRE over IPsec design.

D:Tunnel Mode does not apply at Phase I — Phase I is only for IKE negotiation.

A: The overload bit (OL bit) signals other routers to avoid using the overloaded router as a transit path for Level 2 traffic. However, the overloaded router can still forward Level 1 local area traffic if applicable.

D: The overload bit is commonly used during router bootup to prevent temporary black holes while the router completes its routing protocol convergence and LSDB synchronization.

Why other options are incorrect:

B: CSNP prioritization is not related to overload bit functionality.

C: LSDB synchronization occurs through normal IS-IS mechanisms; overload bit is not involved.

E: The overload bit prevents transit usage, not attracts traffic.

The priority queue (strict priority queue) is intended for real-time, delay-sensitive traffic like voice and certain video, which have:

D. Intolerance to jitter: Real-time traffic requires consistent latency.

E. TCP-based application: Many real-time video streams and some financial trading apps use TCP but still require minimal jitter and latency.

CCDE v3.1 emphasizes that strict priority queue should only be used for traffic highly sensitive to delay and jitter to avoid starving other queues.

Why other options are incorrect:

A: HTTP-like small transactions are delay-tolerant.

B: WRED (Weighted Random Early Detection) is used for congestion avoidance, not prioritization.

C: Priority queue is specifically for traffic intolerant to loss and jitter.

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A (Working design over documentation):Agile prioritizes functional working solutions over exhaustive documentation, allowing continuous delivery and adaptability during the project lifecycle.

Other options explained:

B: Agile favors customer collaboration over contract negotiation.

C: Agile favors responding to change over rigid planning.

D: Agile favors individuals and interactions over processes and tools.