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Router? Bridge? Switch? Hub? What's
the difference? Ever wonder what the difference is among these boxes? Which one do you use when? Let's take a look. We'll start with the simplest device, the Hub. Hub A passive hub serves simply as a conduit for the data, enabling it to go from one device (or segment) to another. So-called intelligent hubs include additional features that enables an administrator to monitor the traffic passing through the hub and to configure each port in the hub. Intelligent hubs are also called manageable hubs. A third type of hub, called a switching hub, actually reads the destination address of each packet and then forwards the packet to the correct port. More info on hubs can be found here.
Bridge With a Bridge, all your computers are in the same network subnet, so you don't have to worry about not being able to communicate between computers or share an Internet connection. DHCP servers will work fine across Bridges, or if you assign your own IP addresses, you'll use the same first 3 "octets" of the IP address (Example: 192.168.0.X) However, the only data that is allowed to cross the bridge is data that is being sent to a valid address on the other side of the bridge. No valid address, no data across the bridge. Bridges don't require programming. They learn the addresses of the computers connected to them by listening to the data flowing through them. Bridges are very useful for joining networks made of different media types together into larger networks, and keeping network segments free of data that doesn't belong in a particular segment. Switches Switches can be used in heavily loaded networks to isolate data flow and improve performance. In a switch, data between two lightly used computers will be isolated from data intended for a heavily used server, for example. Or in the opposite case, in "auto sensing" switches that allow mixing of 10 and 100Mbps connections, the slower 10Mbps transfer won't slow down the faster 100Mbps flow. Although switch prices are dropping so that there is very little difference from hub prices, most home users get very little, if any, advantage from switches, even when sharing broadband Internet connections. Broadband connections for most users are in the 1-2Mbps range, far below even 10Mbps speeds. Since you share that bandwidth, you can see that your speedy 100BaseT connection isn't even breaking a sweat when you're using the Internet.
Router Routers isolate each LAN into a separate subnet, so each network adapter's IP address will have a different third "octet" (Example: 192.168.1.1 and 192.168.2.1 are in different subnets). They are necessary in large networks because the TCP/IP addressing scheme allows only 254 addresses per (Class C) network segment. Routers, like bridges, provide bandwidth control by keeping data out of subnets where it doesn't belong. However, routers need to be set up before they can get going, although once set up, they can communicate with other routers and learn the way to parts of a network that are added after a router is initially configured.
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Routers are also the
only one of these four devices that will allow you to share a single IP
address among multiple network clients.
