Connecting Just Two Computers
If you’re making a network of just two
computers (say, to copy files from an old to a new computer), you might
be able to take a shortcut and eliminate the need for a network switch
or additional special hardware. If you want to add on to your network
later, you can always add the extra gear then.
Note
Microsoft is encouraging the use of a special
USB cable for use by the Windows Easy Transfer program, for people who
don’t have a network. However, you can just as easily (and much less
expensively) use an Ethernet crossover cable.
If you are connecting two computers, simply run a special cable called an Ethernet crossover cable
from one computer’s network adapter to the other, and you’re finished.
This special type of cable reverses the send and receive signals
between the two ends and eliminates the need for a switch. You can
purchase an Ethernet crossover cable from a computer store or network
supply shop, or you can make one, as shown in Figure 4.
Figure 4.
Wiring for a UTP crossover cable. The cable reverses the send and
receive wires so that two network cards can be directly connected
without a switch. Note that the green pair and orange pair are reversed
across the cable.
Tip
Be sure that your crossover cable is labeled
as such. It won’t work to connect a computer to a switch, and you’ll go
nuts wondering what’s wrong if you try. Factory-made models usually
have yellow ends. (When I make them myself, I draw three rings around
each end of the cable with a permanent-ink marker.)
If you have a cable that you’re not sure
about, look at the colors on the little wires inside the clear plastic
connectors at the two ends. Considering just the colors on the wires,
without regard to whether the colors are solid or striped:
• If you can see that each color is in
the exact same position at both ends of the cable, in the arrangement
“AABCCBDD,” you have a standard Ethernet patch cable.
• If a pair of wires that is together
at one end of the cable is split apart at the other end (that is, if
one end has the pattern AABCCBDD and the other has BBACCADD), you have
an Ethernet crossover cable.
• If the pairs of wire are
arranged symmetrically around the center of the connector (that is, if
the pattern is ABCDDCBA), the cable is a telephone cable and not an Ethernet cable. You can’t use this type of cable for networking.
Connecting Multiple Switches
You might want to use more than one switch to
reduce the number of long network cables you need if you have groups of
computers in two or more locations. For example, you can connect the
computers on each “end” of the network to the nearest switch, and then
connect the switch to a main switch. Figure 5 shows a typical arrangement using this technique.
Figure 5.
You can connect groups of computers with multiple switches to reduce
the number of long cables needed. Use the cascade port on the remote
switches to connect to the central switch.
Note
A switch’s uplink or cascade
port is a connector designed to be connected to another switch or hub.
Some switches have a separate connector for this purpose, whereas
others make one of their regular ports do double-duty by providing a
pushbutton that turns the last switch port into a cascade port. Still
others handle this automatically. Refer to your switch’s manual to see
what to do with your particular hardware.
If you need to add a computer to your LAN and
your switch has no unused connectors, you don’t need to replace the
switch. You can just add a switch. To add a computer to a fully loaded
switch, unplug one cable from the original switch to free up a port.
Connect this cable and your new computer to the new switch. Finally,
connect the new switch’s cascade port to the now-free port on the
original switch, as shown in Figure 6.
Figure 6.
You can expand your network by cascading switches. The instructions
included with your switch describe how to connect two switches using a
patch cable. Some switches have a dedicated uplink port, whereas others
have a pushbutton that turns a regular port into an uplink port.
