The core layer is a high-speed switching backbone. If they do not have an associated router module, an external router is used for the Layer 3 function. This layer of the network design should not perform any packet manipulation. Packet manipulation, such as access list filtering, would slow down the switching of packets. Providing a core infrastructure with redundant alternate paths gives stability to the network in the event of a single device failure.

The core can be designed to use Layer 2 or Layer 3 switching. Asynchronous Transfer Mode (ATM) or Ethernet switches can be used.

Interactive Media Activity Point and Click: Core Layer Students completing this activity will be able to identify the key function of the core layer in the three layer design model.

   

Web Links Understanding Network Models – The Cisco Network Design Model http://www.2000trainers.com/ article.aspx?articleID=56&page=1