Hubs and Switches

Hubs and switches are used to connect several hosts together on a star architecture network. They can have any number of connections; the common sizes are 4, 8, 16, 24, and 48 connections (ports)each port has a light that comes on when a network connection is made (link light). Their use enables you to expand your network easily; you can just add new hubs or switches when you need to add new connections. Each unit can connect to the other hubs or switches on the network, typically, through a port on the hub or switch called an uplink port. This enables two hubs or switches, connected by their uplink ports, to act as one hub or switch. Having a central location where all the hosts on your network can connect allows for easier troubleshooting of problems. If one host goes down, none of the other hosts are affected (depending on the purpose of the downed host). Because hubs and switches are not directly involved with the Linux operating system, compatibility is not an issue.

If you are constructing a small to mid-size network, it is important to consider whether you intend to use either hubs or switches. Hubs and switches are visually the same in that they have rows of network ports. However, under the hood, the difference is quite important. Data is sent as packets of information across the network; with a hub the data is transmitted simultaneously to all the network ports, irrespective of which port the destination computer is attached to.

Switches, however, are more intelligent because they can direct packets of information directly to the correct network port that leads to the destination computer. They do this by "learning" the MAC addresses of each computer that is attached to them. In short, using switches minimizes excess packets being sent across the network, thus increasing network bandwidth. In a small network with a handful of computers, the use of hubs might be perfectly acceptable and you will find that hubs are generally cheaper than switches. However, for larger networks of 15 computers or more, you might want to consider implementing a switched network.

Troubleshooting network connections can be a challenge, especially on large networks. If a user complains that he has lost his network connection, the hub is a good place to start. If the link light for the user's port is lit, chances are the problem is with the user's network configuration. If the link light is not on, the host's NIC is bad, the cable is not inserted properly, or the cable has gone bad for some reason.

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