Cisco break up networks into three easy to manage layers to tiers.
Access Layer – Provides workgroup/user access to the network as a result this layer is sometimes called the workstation layer.
Distribution Layer – policy based connectivity and controls the boundary between the access and the core layers
Core Layer – fast transport between distribution switches within the enterprise campus. called the bone layer
- Layer 2 Switching
- Port Security
- QoS classification and marking and trust boundaries
- Spanning Tree
- PoE and auxiliary VLANs for VoIP
- Aggregation of Lan or WAN links
- Policy-based security in the form of ACLs and filtering
- Routing services between LANs and VLANs between routing domains
- Redundancy and load balancing
- Boundary for route aggregation and summarization configured on interfaces towards the core layer.
The Core Layer
- Providing high-speed switching.
- Providing reliability and fault tolerance
Collapsed Core Design takes the functions of the distribution layer and moves them (collapses) them into the core layer.