Cisco Three Tier Architecture

Cisco Three Layer Model

Ø Access Layer

Ø Distribution Layer

Ø Core Layer

Access Layer

     ü  Also called desktop layer

ü  End user are connected

ü  User and resources are locally available

ü  Entry point to the network

ü  Bottom most layer at the Cisco hierarchical model

ü  Devices available are: switches, hubs, etc. 

Distribution Layer 

ü  Primary functions are: -routing, filtering, and WAN access.

ü  Other functions are: -

o   Aggregation of access layer devices;

o   Routing traffic to provide departmental or workgroup access;

o   Segmenting the network in to multiple broadcast/multicast domains;

o   Translating between different media types, such as Token Ring and Ethernet;

o   Providing security and filtering services;

o   After choosing the path, forwards the request to the Core layer. 

Core Layer

ü  Also called backbone layer

ü  Switches traffic to the appropriate service (e.g. e-mail, internet access, videoconfrencing)

ü  Provides quick transport to the desired enterprise service.