ENSLD 300-420 study plan

Map every exam objective in Domain 1 to a one-line note stating what decision the designer must make and what evidence would prove the design correct

Explain the structured design lifecycle (requirements, logical design, physical design, implementation, validation, optimization) and state which artifacts each stage produces

Compare hierarchical three-tier and collapsed-core/leaf-spine campus models, listing at least four criteria for choosing between them

Describe the Cisco PPDIOO and the design-methodology approach at a level where you can justify each phase to a stakeholder

Derive a requirements list from a written business scenario and separate functional, non-functional, and constraint items

Calculate subnet and summarization plans for a given address block and verify them against host counts and growth headroom

Explain how modularity, hierarchy, and summarization reduce failure domains and routing table size, citing at least two concrete design patterns

Produce a design justification that names the trade-off accepted for each major decision (cost, complexity, availability, scalability)

Design a campus VLAN and Layer 2 topology that limits broadcast domains and avoids spanning-tree loops without relying on STP alone

Select and justify first-hop redundancy, stacking versus chassis, and uplink capacity for a given access-layer requirement

Explain STP/RSTP/MST behavior, root bridge placement, and how to bound convergence time in a design document

Describe how Cisco SD-Access fabric roles (control plane, border, edge) map to a campus design and when a fabric is warranted

Design a branch solution that selects between local switching, SD-WAN-integrated routing, and cloud-managed options based on size and criticality

Specify high-availability and path-redundancy options for a branch with a single ISP and justify the residual risk

Plan wireless coverage and capacity assumptions (client density, AP placement, controller versus controller-less) at the design level

Explain how QoS classification and marking should be positioned at campus and branch edges so that trust boundaries are explicit

Compare classic WAN options (MPLS, internet, cellular, metro Ethernet) on SLA, cost, and failover behavior and pick one per traffic class

Design a hybrid WAN that classifies traffic into at least four classes and assigns each a path preference and fallback

Explain SD-WAN architecture components (controller, orchestrator, data plane) and describe how control-plane and data-plane separation affects design choices

Design application-aware routing and SLA-based path selection policies for real-time and bulk traffic, including thresholds

Design a site-to-site and remote-access topology that accounts for encryption, key management, and scale limits of the chosen overlay

Plan WAN addressing, routing adjacencies, and route summarization so that failover converges predictably

Identify where segmentation (VRF, zones, policy) must be enforced across the WAN and describe the enforcement point

Write a failure-mode analysis covering at least five WAN failure scenarios and the expected behavior of each

Describe how model-driven and controller-based automation change design decisions (intent, templates, source of truth) and list the design inputs each requires

Define assurance metrics and telemetry sources that would validate the campus, branch, and WAN designs produced earlier

Explain how network segmentation and policy are expressed as intent in a controller-driven design and where the design must still make explicit choices

Identify design risks introduced by automation (blast radius, drift, dependency on controller availability) and propose mitigations

Reconstruct each domain's objective list from memory and mark any objective you cannot explain in two sentences

Complete at least 120 practice questions across all domains and categorize every miss by domain and by error type (knowledge gap, misread, design trade-off)

Redesign the weakest scenario from weeks 2-7 under a 25-minute time limit and compare it against your original deliverable

Write a one-page exam-day decision checklist covering requirement extraction, trade-off justification, and elimination of answers that violate stated constraints