Cognitive Campus Switching Platforms
This domain covers Arista's campus switch families and the platform features that distinguish them. Know the positioning: fixed-form access switches for wiring closets, higher-density aggregation switches, and PoE-capable models for endpoints like phones, cameras, and APs. Understand PoE fundamentals - PoE/PoE+ power budgets per port and per switch, and how power budgeting affects which ports can deliver full power. Know the difference between fixed and modular platforms and where stacking or MLAG fits.
Concepts to master: MLAG for active-active multi-chassis LAG (peer-link, peer-address, consistent config on both peers), stacking where supported, and the role of the management and console ports. Understand airflow and power redundancy at a high level, and how platform choice maps to port count, uplink speed, and PoE needs.
Traps: (1) Assuming MLAG requires a dedicated peer-link only - the peer-link carries control and can carry data; misconfiguring it causes split-brain symptoms. (2) Forgetting that MLAG peer switches must have consistent VLAN and LAG configuration or the LAG stays down. (3) Confusing PoE class negotiation with actual power draw - budget for worst case. (4) Assuming all campus platforms support the same feature set (stacking, PoE, uplink speeds vary).
Rule of thumb: MLAG = two switches acting as one logical LAG endpoint; the peer-link plus a keepalive path prevents split-brain. Worked example: a wiring closet with 48 PoE+ phones at 25.5 W each needs ~1,224 W of PoE budget - verify the switch's PoE budget exceeds that with headroom, or some ports will be denied power. For uplink redundancy, dual-home the access switch to two aggregation switches running MLAG so the access LAG survives one peer failure.