Timothy
Parker Consulting Incorporated
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Hubs, cables and NICs Our last column had us deciding to install a mix of 10BaseT and 10Base2 Windows, DOS, OS/2, and Unix machines on an Ethernet peer-to-peer TCP/IP network. Before we install the network we need a hub (for the 10BaseT machines to connect to the 10Base2 network) and a bunch of network interface cards. Windows 95 supports plug-and-play, so we could buy any network card that supports Ethernet, has plug-and-play support to set the IRQ, DMA, and so on, and has either an RJ-45 (for 10BaseT) or BNC (for 10Base2) connector for the network cables. As mentioned in the last column, 10BaseT network cards are cheaper than 10Base2 cards, but we’ll use a mix in our example network. There are dozens of network card vendors that offer PCI and ISA cards that do what we want, so we buy our networks cards based on plug-and-play support and the best price we can get. Network cards all are pretty much the same for simple network use, so we’ll use a mix of 3Com, Intel, and SMC. We need a hub, and since we’re being economical we get an unmanaged hub. Allied Telesyn hubs are quite inexpensive and I’ve used dozens with success, although there are many other choices. The final choice for the network is whether we’re going to buy all our network cables pre-made, or buy connector parts and a roll of cable and make our own. Pre-made cables cost more but are already tested and simple to install. Usually there’s a bunch of cable left over to hide between machines and the hub, but the convenience of a pre-made cable can save hours of work. A typical inexpensive pre-made 25-foot cable costs about $15 retail. Bulk cable costs about 50 cents a meter or more depending on quality, and must be purchased in rolls of at least 500 feet. You need category 5 cable. Rolls of 1000 feet are about $140 for cheap cable, and up to $500 for good stuff. If the network is small and the machines are not more than 50 feet from the hub, get cheap cable! If you decide to make your own cables, you need to buy a reel of bulk cable, connectors, and tools. For 10BaseT cables, there are bags of RJ-45 connectors available cheap, but you’ll need a crimping tool with a die set, which runs anywhere from $25 to $100 depending on manufacturer and quality. For 10Base2 cables, a pair of pliers or crimpers and wire strippers are all you need, along with a bag full of BNC connectors parts. If you’re going to do a lot of network installations, a cable tester is a nice tool to show if the cable you just installed has a problem, but these devices tend to be expensive. Is it worth making your own cables? If you are doing a ten machine network, you can save a few hundred dollars by doing your own cables (not including the acquisition cost of the tools and left-over cable). However, the chances of a bad cable are much higher, and the time to construct the cables can add up to a couple of hours. You have to decide between cost, time, and convenience. Pre-made cables can be obtained in a wide variety of lengths, are pre-tested, and tend to be better constructed than most hand-made cables. If the customer is willing to pay for pre-made, that’s the way to go. The next step is to work out an identity for each machine on the network. The network as a whole has a workgroup name or a domain (the later with Unix networks, usually), and each machine has both a name and a unique IP address. For our network all the machines are in the same workgroup for convenience. As mentioned, you need a unique IP address for each machine. This is a set of four numbers such as 205.150.89.10 (called dotted-quad notation) that identifies not only the network but also each machine on the network. If the network is to be connected to the Internet or another network, you need an approved IP address which requires a fee and form to a Virginia-based company that handles all the network addresses. You’ll be assigned a set of numbers depending on the size of your network. We haven’t go room here to go into details about network classes, so check my TCP/IP series from last year or any TCP/IP or networking book (especially mine!). Let’s install the network cards in the Windows 95 machines to get this network on the roll. Open each Windows 95 machine and drop in one of your plug-and-play network cards. Most network cards available today are PCI, and they are faster than ISA network cards. Many network cards also support 100Mbps networks, which gives the network the chance to run at ten times the normal speed if all machines have 100Mbps cards and the hub supports it. When Windows 95 is rebooted, the operating system detects the presence of most network cards and either prompts for the Windows 95 installation CD-ROM or the driver disk that accompanies most network cards. Windows 95 manages to choose network card settings that are trouble-free about 99% of the time, but every now and again there is some device which mucks things up. If that’s the case, you will have to change the IRQ and address in the Windows 95 System Control Panel. (A tip many VARs don’t seem to know about: you can see which IRQ, DMA, and I/O addresses are in use from the My Computer Properties page, select the Device Manager page, and click on the Properties button at the bottom of the screen. This lets you see all the system resources already assigned and in use.) If you are using non-plug-and-play cards, or want to set configuration information yourself, you need to configure the network card with the utilities most manufactureres include on a diskette. Some older cards use jumpers or DIPs to set IRQ and address, in which case when Windows 95 asks about the card, you can supply this information. In a few cases, Windows 95 won’t recognize the card at all and you’ll have to add it manually through the Add Hardware Control Panel option. You won’t be able to test the network card until the network is installed, but after a reboot the Windows 95 System window should show that the network card is working properly. |
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