Hubs, Switches, Bridges, Routers and Gateways

There are a number of networking components out there, and choosing what you need can be confusing. This article is designed to give you an overview of the most common networking technologies in use today.

HUBS AKA REPEATERS

Hubs (also called repeaters) are simple and inexpensive devices used to connect networked workstations together, and extend the power of network signals. Network cables all suffer from what is called signal attenuation. The farther a signal travels, the weaker it gets. A hub (repeater) boosts the signal, and renews it’s strength to make sure it gets where it is going and at a strength that is still readable. Hubs are very easy to set up: Just plug the network cables in, and off you go.

Hubs do not filter data and therefore every packet of information sent out through the hub is passed along to every computer, which can become an issue on hard working networks, where bandwidth and speed is an issue. Virtually all hubs come with a series of LEDs that can be consulted to see which computers are online and working and which are not. Quite often when a workstation loses all contact with the network, it is a burned out port on the hub, or failed network interface card. The absence of any LED activity of the hub for the offending workstation can confirm this. Hubs cannot join dissimilar types of LANs (Ethernet to Token Ring, etc.).

SWITCHES

Switches are a fairly new technology and are often used in place of hubs, especially on networks where network bandwidth and speed are issues. A switch is capable of reading incoming packets and only sending those packets to the computers to which they are addressed thereby reducing network traffic. Switches cannot join dissimilar types of LANs (Ethernet to Token Ring, etc.).

BRIDGES

Bridges, like switches, are capable of filtering data packets and only sending packets to the computers for which they are addressed. The most common form of bridge today is the learning bridge, which over time learns which computer is where, what each computer’s unique address is (just like your mailing address) and who receives what, although bridges lack the ability to determine which routes are the fastest. A learning bridge is not as fast as a switch, and has far fewer ports. Many companies are abandoning bridges in favor of switches. Bridges cannot join dissimilar types of LANs (Ethernet to Token Ring, etc.).

ROUTERS

Routers are more intelligent that bridges. All routers maintain a routing table of paths that data can travel, and can be configured to send specific data packets down specific routes to maximize speed. Routers come in two types: Static and dynamic. Static routers require the network administrators to program the routing table. Dynamic routers periodically check all available routes and are capable of building their own routing tables and learning the fastest routes for data travel. Routers can join dissimilar networks, filter packets to decrease the overall load on the network. A router requires the use of routable protocols like TCP/IP and IPX/SPX. NetBEUI will not work with a router.

BROUTERS

A brouter does everything a router does, but also has the bridge-like capability of handling non-routable protocols like NetBEUI. If your network uses a combination of routable and non-routable protocols, then a brouter is your best choice. It should be noted that virtually all routers manufactured today ARE brouters. The distinction is breaking down, and the term brouter is disappearing from common use.

GATEWAYS

Once used as an alternative term for a router, the term is now applied to any system on the network that can connect different networks using different protocols. A gateway can strip off protocol specific information from a data packet and replace it with protocol specific information from an entirely different protocol standard. In other words, a gateway allows a network using IPX/SPX to talk to a network using TCP/IP.

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