Collapsed Core & Three Tier Architecture (CRAM Notes)

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

Access Layer

  • Layer 2 Switching
  • Port Security
  • QoS classification and marking and trust boundaries
  • ARP
  • VACLs
  • Spanning Tree
  • PoE and auxiliary VLANs for VoIP

Distribution Layer

  • 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.


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