Lan Design

For the small- and medium-sized business, communicating digitally using data, voice, and video is critical to business survival. Consequently, a properly designed LAN is a fundamental requirement for doing business today. You must be able to recognize a well-designed LAN and select the appropriate devices to support the network specifications of a small- or medium-sized business.
In this chapter, you will begin exploring the switched LAN architecture and some of the principles that are used to design a hierarchical network. You will learn about converged networks. You will also learn how to select the correct switch for a hierarchal network and which Cisco switches are best suited for each network layer. The activities and labs confirm and reinforce your learning
The Hierarchical Network Model:
When building a LAN that satisfies the needs of a small- or medium-sized business, your plan is more likely to be successful if a hierarchical design model is used. Compared to other network designs, a hierarchical network is easier to manage and expand, and problems are solved more quickly.
Hierarchical network design involves dividing the network into discrete layers. Each layer provides specific functions that define its role within the overall network. By separating the various functions that exist on a network, the network design becomes modular, which facilitates scalability and performance.
Access Layer
The access layer interfaces with end devices, such as PCs, printers, and IP phones, to provide access to the rest of the network. The access layer can include routers, switches, bridges, hubs, and wireless access points. The main purpose of the access layer is to provide a means of connecting devices to the network and controlling which devices are allowed to communicate on the network.
Distribution Layer
The distribution layer aggregates the data received from the access layer switches before it is transmitted to the core layer for routing to its final destination. The distribution layer controls the flow of network traffic using policies and delineates broadcast domains by performing routing functions between virtual LANs (VLANs) defined at the access layer. VLANs allow you to segment the traffic on a switch into separate subnetworks. For example, in a university you might separate traffic according to faculty, students, and guests. Distribution layer switches are typically high-performance devices that have high availability and redundancy to ensure reliability. You will learn more about VLANs, broadcast domains, and inter-VLAN routing later in this course.
Core Layer
The core layer of the hierarchical design is the high-speed backbone of the internetwork. The core layer is critical for interconnectivity between distribution layer devices, so it is important for the core to be highly available and redundant. The core area can also connect to Internet resources. The core aggregates the traffic from all the distribution layer devices, so it must be capable of forwarding large amounts of data quickly.


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