Campus Switching Architecture and Device Deployment
Design roles and deployment choices
Aruba campus designs usually separate access, aggregation/distribution, and core layers, though small sites collapse distribution and core. Access switches provide PoE and VLAN edge ports; aggregation devices terminate access uplinks, host Layer 3 gateways or VSX/VSF pairs, and apply policy; core devices provide high-speed transit between aggregation blocks and the data center. Candidates should know the CX portfolio families and when a fixed-form switch versus a modular chassis is appropriate, plus stacking versus standalone operation. Deployment topics include out-of-band management, management VRF, in-band management VLANs, ZTP/DHCP options, Central onboarding, firmware consistency, licensing, redundant power, airflow, and PoE budget.
Traps: confusing the distribution layer's role with pure core transit; assuming all PoE ports can deliver maximum class power simultaneously; ignoring management-plane separation; and treating VSF/VSX as a substitute for routed design. Also verify ZTP prerequisites (DHCP, option 60/66/67 or Central) and that stacking cables and uplinks are not oversubscribed.
Worked example/rule of thumb: PoE budget. A 48-port access switch with a 740 W PoE budget cannot power 48 ports at 802.3at Type 2 (30 W): 48 × 30 = 1440 W. Even 48 × 15.4 W = 739 W leaves essentially no margin. Rule of thumb: size access uplinks for expected oversubscription (often 10:1 to 20:1 for user access) and reserve 20-30% PoE headroom.