In preparation of our CCNA exam, we want to make sure we cover the various concepts that we could see on our Cisco CCNA exam. So to assist you, below we will discuss Cisco CCNA 3 Layer Model.
The Cisco CCNA exam has been designed to prepare you for the real world of managing a large network and that can be a very complicated procedure. There are many factors to bring into consideration when designing a network’s topography; traffic, WAN support, speed, reliability, cost, and more. This is where Cisco’s Three-Layer Hierarchical Model proves to be an invaluable asset to establishing a fast, dependable, scalable, and cost-effective internetwork. You will definitely want to make sure you are familiar with this for your CCNA exam. The three layers include Core, Distribution, and Access, and they each provide their own purpose. Using this model, it is possible to create a network that is designed in a predictable way, is easily maintained and efficient to the effect of troubleshooting, leaves plenty of room for future expansion of the network or network services, and can manage the most possible functionality in a wide range of applications.
The Core Layer is effectively the backbone of the Hierarchical Model. This layer provides fast and efficient switching of mass amounts of data to the whole operation. This layer must be designed with speed and low latency (time between receiving and transmitting a packet) in mind. It’s important that changes made to this layer be made with concern to the notion that this is the top layer; anything affecting this layer is likely to affect all users across the board. This in mind, fault-tolerance and speed are essential at the Core Level. Avoid using any access lists or packet filters at this level. These will be used at the Distribution Layer and may cause problems if implemented in the Core Layer.
The Distribution Layer, or Workgroup layer as it is sometimes known, provides routing filtering, and WAN services, acting as a go-between for the Access Layer and the Core. The Distribution Layer also determines how packets will access the core, using the fastest and most reliable method possible. This layer will be used to implement network policies, such as address translation, firewalls, and filtering. The Distribution Layer will negotiate requests between the Access Layer, to which all workgroup members are connected, and the Core Layer, which will direct the request to the proper service and provide access if necessary to the Access Layer.
The Access Layer, or Desktop Layer, controls local user access to workgroup resources on the internetwork. The network at this level will be segmented into separate collision domains, allowing for smooth transmission to each host. There is continued management of access control and policy at this layer, a task that is shared between the Access Layer and the Distribution Layer. Static routing and DDR/Ethernet Switching are commonly implemented in this layer as well.
Summarily, the Cisco Three-Layer Hierarchical Model establishes standards for designing a reliable and fast internetwork. It is a tool that has been provided to ensure some predictability in topography and network theory. This layered approach should also be understood as a logical layering, not a physical one, meaning it is not necessary there be 3 routers performing each of these functions separately. There may be multiple devices performing single-layer functions, or there may be functions of different layers being performed by one or two devices. Each of these layers, with their specific functions, is integral to the overall deployment of a productive and powerful network. If you are familiar with these concepts, you are one topic down on your way to your CCNA certification!
I hope you found this article to be of use and it helps you prepare for your Cisco CCNA certification. Achieving your CCNA certification is much more than just memorizing Cisco exam material. It is having the real world knowledge to configure your Cisco equipment and be able to methodically troubleshoot Cisco issues. So I encourage you to continue in your studies for your CCNA exam certification.