Explanation/Reference:
Large-Building LANs
Large-building LANs are segmented by floors or departments. The building-access component serves one
or more departments or floors. The building-distribution component serves one or more building- access
components. Campus and building backbone devices connect the data center, building-distribution
components, and the enterprise edge-distribution component. The access layer typically uses Layer 2
switches to contain costs, with more expensive Layer 3 switches in the distribution layer to provide policy
enforcement. Current best practice is to also deploy multilayer switches in the campus and building
backbone.
Cisco Enterprise Architecture Model
Core
Distribution
Access
Cisco Press CCDA 640-864 Official Certification Guide Fourth Edition, Chapter 3