A three-tier model of network design is a proven and well-known basic architecture, which is widely used for campus networks. Core-layer switches make up the top layer or core of the network. Each layer is served by specialized switches, with the access switch connecting end-user devices, the distribution switch aggregating traffic and enforcing policies, and the core switch acting as. The three layers of a traditional three-layer network design are the core layer, aggregation layer, and access layer. Access Layer - Endpoint connectivity and PoE power engineering (IEEE 802. Aggregation Layer - Inter-VLAN routing, policy enforcement, bandwidth. In a three-layer hierarchical model for Cisco routers, The first layer is the local area network (LAN) that uses I EEE 802.