Campus and Branch Wired/Wireless Design
Campus wired fundamentals
Candidates should be fluent in hierarchical campus design: access layer for endpoint attachment and PoE, distribution for policy and inter-VLAN routing, core for high-speed aggregation. Understand spanning-tree avoidance strategies (L3 access, MLAG/VSX-style multichassis aggregation), link aggregation, and the trade-offs of large L2 domains versus routed access. Know PoE budgeting (per-port and per-switch), uplink oversubscription, and stacking versus chassis versus standalone designs.
Wireless design is RF plus network
Wireless questions test both radio and network planning. Know how to translate a capacity requirement (clients per area, throughput per client) into AP count, and how coverage requirements differ from capacity requirements. Understand channel planning in 2.4/5/6 GHz, channel width trade-offs, co-channel interference, and why 6 GHz changes planning (more channels, shorter range). Know the roles of a mobility controller/gateway versus controller-less or cloud-managed architectures, and where tunneling versus local breakout applies. Roaming (L2 vs L3), fast roaming mechanisms, and guest isolation are common topics.
Branch design
Branch designs balance cost and resilience: local switching with centralized policy, SD-WAN for transport flexibility, and survivability when the WAN fails (local DHCP/DNS, local authentication, local internet breakout). Traps include designing for coverage when the requirement is density, ignoring uplink oversubscription, and forgetting that a branch device failure may strand local services.
Worked example
A 200-seat floor needs 2 Mbps per client at peak with 60 concurrent clients. That is 120 Mbps of aggregate demand; at a realistic per-AP effective throughput of ~300 Mbps in 5 GHz, two APs cover capacity, but coverage and redundancy usually push the count higher. Design to the larger of coverage and capacity, then verify channel reuse.