-Tier 2 Design-
Known as collapsed core – in which the distribution layer and core layer functions are implemented in single device. Commonly used in small enterprise networks which does not grow significantly in next few years.
Distribution/Core layer provides connectivity to:
- WAN edge
- Internet edge
- Network services
- LAN aggregation to the end- user access layer
Access layer provides connectivity to:
- End-users or Endpoints Access
-Tier 3 Design-
Has separate core and distribution layers. Commonly implemented in large enterprise networks with multiple buildings.
Core Layer provides connectivity to:
- WAN edge
- Internet
- Network service
- Data Center
- Distribution Layer
Distribution layer provides:
- Policy-based connectivity and boundary control between access and core layers.
Access layer provides connectivity to:
- End-users or Endpoints Access
WAN Edge – used to connect to remote data centers, remote branches or other campus networks.
Internet Edge – used for regular internet access, remote VPN Access or cloud connectivity which does not requires dedicated interconnections
Network services – is where the devices providing the network services located. For example, Wireless Controllers, Cisco Identity Services Engine (ISE), Cisco Unified Communications Manager (CUCM), and others.
Wired-Me-Not 