Access, distribution, and core layers

Cisco's three-layered architecture helps defining the enterprise networks by simplifying the process of designing a reliable, highly-redundant, and scalable hierarchical inter-network. The three layers of Cisco architecture are as follows:

• Access layer, as the name indicates, is the layer in which network services are accessed. This layer mainly consists of computers, servers, hubs, layer 2 switches, access points, and other network end devices. A LAN network can be considered as an access layer analogy.
• Distribution layer is the middle layer that plays the role of the bridge by interconnecting the access layer and the core layer. This layer mainly uses layer 3 switches and routers. Extended LANs that form the MAN can be considered as a distribution layer analogy.
• Core layer is a fast and highly redundant network that is managed by core switches and routers. It is a backbone of the corporate network that enables the packet's movement between distribution-layer devices in different segments of the network. A WAN network can be considered as a core layer analogy.