Network hardware

Ethernet hub

In data comms, a hub is a place of convergence where data arrives from one or more directions and is forwarded out in one or more other directions. A hub usually includes a switch of some kind (and a "switch" product can usually be considered a hub as well). The distinction seems to be that a hub is the place where data comes together and a switch is what determines how and where data is forwarded from the place where data comes together. In its switching aspects, a hub can also include a router.

Note that a hub has no in-built security.


In a telecomms network, a switch is a device that channels incoming data from any of multiple input ports to the specific output port that will take the data toward its intended destination. In the traditional circuit-switched telephone network, one or more switches are used to set up a dedicated though temporary connection or circuit for an exchange between two or more parties. On an Ethernet local area network (LAN), a switch determines from the physical device (Media Access Control or MAC) address in each incoming message frame which output port to forward it to and out of. In a WAN such as the Internet, a switch determines from the IP address in each packet which output port to use for the next part of its trip to the intended destination.

In the Open Systems Interconnection (OSI) model, a switch performs the layer 2 or Data-Link layer function. That is, it looks at each packet or data unit and determines from a physical address (the MAC address) which device a data unit is intended for and switches it out toward that device. However, in wide area networks (WANs) such as the Internet, the destination address requires a look-up in a routing table by a device known as a router. Some newer switches also perform routing functions (layer 3 or the Network layer functions in OSI) and are called IP switches.


On the Internet, a router is a device or, in some cases, software in a computer, that determines the next network point to which a packet should be forwarded toward its destination. Thus the router is connected to at least two networks and decides which way to send each packet based on its current understanding of the state of the networks it is connected to. A router is located at any gateway including each Internet point-of-presence. A router is often included as part of a network switch.

A router that incorporates Network Address Translation (NAT) provides an in-built firewall on the internet connection.

A summary of the Differences Between an Ethernet Hub or Switch and a Broadband Router is useful considering when and where each device should be used.


In telecomms networks, a bridge is a product that connects a LAN to another LAN that uses the same protocol (e.g. Ethernet or Token Ring). A bridge works at the data-link (physical network) level of a network, copying a data frame from one network to the next network along the communications path. A bridge is sometimes combined with a router in a product called a brouter.


A brouter is a network bridge and a router combined in a single product. A bridge is a device as defined above. If a data unit on one LAN is intended for a destination on an interconnected LAN, the bridge forwards the data unit to that LAN; otherwise, it passes it along on the same LAN. A bridge usually offers only one path to a given interconnected LAN. A router connects a network to one or more other networks that are usually part of a WAN and may offer a number of paths out to destinations on those networks. A router therefore needs to have more information than a bridge about the interconnected networks. It consults a routing table for this information.


A gateway is a network point that acts as an entrance to another network. On the Internet, a node can be either a gateway node or a host (end-point) node. Both the computers of Internet users and the computers that serve pages to users are host nodes. The computers that control traffic within your company's network or at your local Internet service provider (ISP) are gateway nodes. For example, all of the hops on a traceroute, except from your PC and the destination host, are gateways.

Network Interface Card (NIC)

A Network Interface Card (NIC) is a computer circuit board or adaptor card that is installed in a computer so that it can be connected to a network. Personal computers and workstations on a Local Area Network (LAN) typically contain a NIC specifically designed for the LAN transmission technology, such as Ethernet or Token Ring. NICs provide a dedicated, full-time connection to a network. Previously most home and portable computers connect to the Internet through as-needed dial-up connection, with the modem providing the connection interface to the Internet service provider. Now, with the advent of broadband, a NIC is the most frequent means of accessing the Interent through a LAN to a shared broadband connection.

CAT5 Cabling

There are two main categories of CAT5 or CAT5e cables used for general networking: straight-through cables and cross-over cables.

The CAT5 or CAT5e standard cable (sometimes also called UTP - UnTwisted Pair, or simply Etherent cable) is available as either cross-over or straight-through. RJ-45 connectors are the standard. The cable configuration and pint-outs are shown in the following links:

The straight-through CAT5/CAT5e is by far the more common cable of the two. The straight-through cable is used if connecting a PC to a router/switch/hub. See cable diagram for some simple diagrams. The connection of a PC to a router/switch/hub) is actually the conneciton of the Network Interface Card (NIC) in the PC.

The rate at which data will transfer depends on both NICs. If one is 10Mbpbs and one is 100Mbps then the data rate is governed by the slower card. If both are 100Mbps then you'll get the higher rate.

If there are only 2 PCs directly connected then the cross-over CAT5 cable is required.

CAT6 Cabling

The next step up from Cat5 cabling is CAT6 or Gigabit Ethernet. More expensive of course, and if 10/100 routers, switches, hubs or NICs are being used then not worth the extra expense.

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