Architecture and Design
Design fundamentals
Aruba campus design starts from a small set of decisions that cascade through everything else: the number of tiers, whether the design is routed-access or a traditional core/aggregation/access model, how large each Layer 2 domain is, and where the control plane for wireless lives. Aruba's recommended modern pattern is a two-tier collapsed core with Layer 3 access (routed access) using VSX for core redundancy and VSF for access switch stacking. Know the roles: core provides the default gateway and routing, aggregation (if present) terminates distribution, access provides PoE and edge ports.
Sizing and capacity
Candidates must be able to translate requirements into hardware. Key numbers: PoE budget per switch and per port class, uplink oversubscription ratios (Aruba guidance is typically around 4:1 for access-to-aggregation), and the number of access points per controller or gateway. Design questions often hinge on choosing between a gateway cluster and a centralized controller, or between 1G and 10G/multigig uplinks for Wi-Fi 6/6E access points.
Traps
- Confusing VSF (stacking, single control plane) with VSX (two independent control planes with a sync link).
- Assuming a design must be three-tier; Aruba frequently prefers a collapsed two-tier model.
- Forgetting that routed access changes how roaming and Layer 2 services behave.
- Ignoring RF design (AP placement, channel plan, coverage overlap) in favor of pure switching design.
Rule of thumb
If a requirement mentions "simplify", "reduce spanning tree", or "fast convergence", lean toward routed access with VSX at the core. If it mentions "single management IP" or "stack", lean toward VSF at the access layer.