Sean Odom, Hanson Nottingham - Cisco Switching Black Book
||Cisco Switching Black Book
||Sean Odom, Hanson Nottingham
||The first local area networks (LANs) began as a result of the introduction of personal computers into the
workplace environment. As computers became more common, the need arose to share resources, such as
printers or files. These early networks were pretty simple, with a handful of computers sharing a few printers
and not much more. As more items such as servers, applications, and peripherals came along, the increasing
numbers of interfaces—along with application designs that could take advantage of the network—created a
weakness in the current network design.
The limitations of traditional Ethernet technology brought forth a number of innovations that soon became
standard in the Ethernet protocol. Innovations such as full duplexing, Fast Ethernet, and Gigabit Ethernet
began to appear—innovations that have also made possible a transition to switches from shared hubs.
Other limitations to the way networks operated in a shared environment created a need for alternative methods
to permit the use of bandwidth−intensive applications such as video and voice. Switches are one of these
alternative methods. In many respects, switches are relatively simple devices. A switch’s design and
self−learning features require very little manual configuration to get it up and running. To properly use these
devices in your network, you must have an in−depth knowledge of the issues involved in implementing
Knowing the basics of Ethernet technology can help you effectively troubleshoot and install switches in the
network. You also need a good grasp of the different technologies and how switches work, as well as the
constraints of each type of device you may use in the network. As you read the following sections, make sure
you get a clear understanding of the fundamentals and basics of Ethernet technology.
The types of devices you use in the network have important implications for network performance. For
example, bridges and routers are both devices that network administrators use to extend the capabilities of
their networks. Both of them have advantages and disadvantages.
Bridges, for example, can easily solve distance limitations and increase the number of stations you can have
on a network, but they can have real problems with broadcast traffic. Routers can be used to prevent this
problem, but they increase the time it takes to forward the traffic.
This has been the pattern throughout the history of networking. When a new product is introduced, problems
or bottlenecks are soon found that limit the product’s usefulness. Then, innovations are invented or
implemented to aid the product and allow it to perform better. To see this occurrence in action, let’s take a
look at some of the traditional network architectures. As you will see in upcoming sections, the pattern of new
innovation after new innovation started in the earliest days of networking and continues in today’s networks.
Network designers from the beginnings of networking were faced with the limitations of the LAN topologies.
In modern corporate networks, LAN topologies such as Ethernet, Token Ring, and FDDI are used to provide
network connectivity. Network designers often try to deploy a design that uses the fastest functionality that
can be applied to the physical cabling.