CCDE 400-007 Cisco Study Notes

PortFast is a feature that allows access ports to enter the STP forwarding state immediately, without waiting for the usual listening and learning states. This accelerates the connection of end devices like PCs or servers.

A key design benefit is that PortFastdoes not trigger topology changeswhen devices are plugged in or disconnected. This prevents unnecessary STP recalculations and protects core stability.

Correct Statement (A):STP does not consider link transitions on PortFast-enabled ports as topology changes, reducing control-plane overhead.

Other options misrepresent the function of PortFast:

B:PortFast does not disable STP; it bypasses specific STP states.

C/D/E/F:These describe other features like Loop Guard or UDLD, not PortFast.

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D: Traditional three-tier architectures (access, distribution, and core layers) require that east-west traffic (between servers or pods in different access layers) traverse up to the distribution or core and then back down—introducing unnecessary hops and latency. This is a key design limitation addressed by spine-leaf and fabric architectures.

Other options:

A: Bandwidth may be sufficient but not optimally utilized due to suboptimal pathing.

B: Security is not inherently compromised by architecture, although microsegmentation is harder.

C: Three-tier architectures can scale, but less efficiently and not without trade-offs like latency and complexity.

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For EIGRP to maintain loop-free alternate paths, the feasibility condition must be met:

A. The Reported Distance (RD) must be lower than the router's Feasible Distance (FD).

E. A feasible successor must exist (i.e., an alternate next-hop satisfying the feasibility condition).

This design allows immediate failover without recomputation, ensuring fast convergence — a critical CCDE v3.1 protocol design principle.

Why other options are incorrect:

B, C, D: Misstate the feasibility condition or confuse RD and FD relationships.

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Agile project management supports:

Frequent updates and iterative feedback loops

Flexibility to accommodate evolving requirements

Continuous customer collaboration and transparency

This methodology is ideal for projects where scope may shift and customer involvement is essential. In contrast:

Waterfall is linear and rigid

Phased delivery segments milestones but limits change midstream

“Three principles” is not a recognized methodology in this context

Agile aligns with modern IT deployment models and is supported in CCDE methodology as a business-aligned and adaptive design execution strategy.