Twinkies
If left sealed in their little individually wrapped packages, Twinkies keep for years. In fact, they’ll probably outlast the network itself. You can bequeath
’em to future network geeks, ensuring continued network support for genera- tions to come.
Extra Network Cards
Ideally, you want to use identical network cards in all your computers. But if the boss’s computer is down, you’d probably settle for whatever network
card the corner network street vendor is selling today. That’s why you should always keep at least one spare network card in the closet. You can rest easy
knowing that if a network card fails, you have an identical replacement card sitting on the shelf, just waiting to be installed — and you won’t have to buy
one from someone who also sells imitation Persian rugs.
Obviously, if you have only two computers on your network, justifying spend- ing the money for a spare network adapter card is hard. With larger networks,
it’s easier to justify.
The Complete Documentation of the Network on Tablets of Stone
I’ve mentioned several times in this book the importance of documenting your network. Don’t spend hours documenting your network and then hide
the documentation under a pile of old magazines behind your desk. Put the binder in the closet with the other network supplies so that you and every-
one else always know where to find it. And keep backup copies of the Word, Excel, Visio, or other documents that make up the network binder in a fire-
proof safe or at another site.
Don’t you dare chisel passwords into the network documentation, though. Shame on you for even thinking about it
If you do decide to chisel the network documentation onto actual stone tablets, consider using sandstone. It’s attractive, inexpensive, and easy to
update just rub out the old info and chisel in the new. Keep in mind, how- ever, that sandstone is subject to erosion from spilled Diet Coke. Oh, and
make sure that you store it on a reinforced shelf.
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The Network Manuals and Disks
In the land of Oz, a common lament of the Network Scarecrow is, “If I only had the manual.” True, the manual probably isn’t a Pulitzer Prize candidate, but
that doesn’t mean you should toss it in a landfill, either. Put the manuals for all the software you use on your network where they belong — in the closet with
all the other network tools and artifacts.
Likewise the disks. You may need them someday, so keep them with the other network stuff.
Ten Copies of This Book
Obviously, you want to keep an adequate supply of this book on hand to dis- tribute to all your network users. The more they know, the more they stay off
your back. Sheesh, 10 copies may not be enough — 20 may be closer to what you need.
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Chapter 29
Ten Network Gizmos Only Big Networks Need
In This Chapter
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Repeaters
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Managed switches
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Bridges
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Gateways
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RAIDs
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Server farms
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Gigabit Ethernet
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Protocol analyzers
P
eople who compile statistics on things — such as the ratio of chickens to humans in Arkansas and the likelihood of the Mets losing when the other
team shows up — report that more than 40 percent of all networks have fewer than ten computers and that this percentage is expected to increase in coming
years. A Ross Perot-style pie chart would be good here, but my editor tells me I’m running long, so I have to pass on that.
The point is that if you’re one of the lucky 40 percent with fewer than ten com- puters on your network, you can skip this chapter altogether. Here, I briefly
describe various network gizmos that you may need if your network is really big. How big is big? There’s no hard-and-fast rule, but the soft-and-slow rule
is that you should look into this stuff when your network grows to about 25 computers.
The exceptions to the soft-and-slow rule are as follows: 1 Your company has two or more networks that you want to hook together, and these networks
were designed by different people who refused to talk to each other until it was too late; 2 your network needs to connect computers that are more than a
few hundred yards apart, perhaps in different buildings or via the Internet.
Repeaters
A repeater is a gizmo that gives your network signals a boost so the signals can travel farther. It’s kind of like the Gatorade stations in a marathon. As the
signals travel past the repeater, they pick up a cup of Gatorade, take a sip, splash the rest of it on their heads, toss the cup, and hop in a cab when
they’re sure no one is looking.
You need a repeater when the total length of a single span of network cable is larger than the maximum allowed for your cable type:
Cable Maximum Length
10Base2 coax 185 meters or 606 feet
10100BaseT twisted-pair 100 meters or 328 feet
For coax cable, the preceding cable lengths apply to cable segments, not indi- vidual lengths of cable. A segment is the entire run of cable from one termina-
tor to another and may include more than one computer. In other words, if you have ten computers and you connect them all with 25-foot lengths of thin coax
cable, the total length of the segment is 225 feet. Made you look Only nine cables are required to connect ten computers — that’s why it’s not 250 feet.
For 10BaseT or 100BaseT cable, the 100-meter length limit applies to the cable that connects a computer to the hub or the cable that connects hubs to each
other when hubs are daisy-chained with twisted-pair cable. In other words, you can connect each computer to the hub with no more than 100 meters of
cable, and you can connect hubs to each other with no more than 100 meters of cable.
You can use a repeater to connect two groups of computers that are too far apart to be strung on a single segment. When you use a repeater like this, the
repeater divides the cable into two segments. The cable length limit still applies to the cable on each side of the repeater.
Here are some points to ponder when you lie awake tonight wondering about repeaters:
⻬ Repeaters are used only with Ethernet networks wired with coax cable. 10100BaseT networks don’t use repeaters.
Actually, that’s not quite true: 10100BaseT does use repeaters. It’s just that the repeater isn’t a separate device. In a 10100baseT network, the
hub is actually a multiport repeater. That’s why the cable used to attach each computer to the hub is considered a separate segment.
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⻬ Some 10100BaseT hubs have a BNC connector on the back. This BNC connector is a Thinnet repeater that enables you to attach a full 185-
meter Thinnet segment. The segment can attach other computers, 10BaseT hubs, or a combination of both.
⻬ A basic rule of Ethernet life is that a signal cannot pass through more than three repeaters on its way from one node to another. That doesn’t
mean you can’t have more than three repeaters or hubs, but if you do, you have to carefully plan the network cabling so that the three-repeater
rule isn’t violated.
⻬ A two-port 10Base2 repeater costs about 200. Sheesh I guess that’s one of the reasons fewer people use coax cable these days.
⻬ Repeaters are legitimate components of a by-the-book Ethernet network. They don’t extend the maximum length of a single segment; they just
enable you to tie two segments together. Beware of the little black boxes that claim to extend the segment limit beyond the standard 185-meter
limit for Thinnet. These products usually work, but playing by the rules is better.
Managed Switches
A managed switch is a 10BaseT or 100BaseT switch that allows you to moni- tor and control various aspects of the switch’s operation from a remote com-
puter. Here are some of the benefits of managed switches:
⻬ Managed switches can keep network usage and performance statistics, so you can find out which parts of your network are heavily used and
which are not. ⻬ A managed switch can alert you when something goes wrong with your
network. In fact, the management software that controls the switch can even be configured to send you e-mail or dial your pager when a network
error occurs. ⻬ You can reconfigure a managed switch from any computer on the net-
work, without having to actually go to the switch. Inexpensive switches do not include management features. An unmanaged
switch is fine for a small network, but for larger networks, you should invest in managed switches. A typical managed switch can cost two or three times
as much as an equivalent unmanaged switch, but for larger networks, the bene- fits of switch management are well worth the additional cost. However, if your
network has only one or two switches, you probably don’t need management.
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