Workshop

designation is simply an industry-standard way of referring to the manufacturing specifications of the
cable. CAT-V can hold a lot more signal than CAT-III; therefore, you can run 10Mb Ethernet on CAT-V
wiring, but you cannot run 100Mb Ethernet on CAT-III. If you’re trying to run 100Mb Ethernet on CAT-
III wiring, you’re going to run into problems.
Don’t try running 100Mb Ethernet on wiring that’s not certified as CAT-V. The world may not come to
an end, but it still will be bad.
All sorts of intermittent network errors can occur, which can domino into your applications. What’s more,
because you’re getting a signal and are talking to the network, you might not realize that the problem is
due to wiring until you’ve run around looking at everything else.
Other than that, 100Mb Ethernet is pretty much the same as 10Mb Ethernet, but faster. For example, the
maximum cable run for either one is 100 meters (330 feet). Both use RJ-45 connectors, and both require
a hub or a switch.
How do you know whether your cable is CAT-V? Well, if it has been installed any time from 1997 on,
you can guess that it’s probably CAT-V. The only way you know is to ask your installer, or to have him
or her test it with a cable scanner. I’ll talk briefly about cable scanners in Hour 21, “Tell Me About Your
Network: Network Analyzers & Bits & Bytes.”
A cable plant fails CAT-V certification in at least five ways, so you should ask the installer to “certify” it
as part of the installation process. This means that he or she will install using plugs, jacks, cabling, and
techniques that are CAT-V compliant and will actually put a meter on the end-to-end product to ensure
that theory has become practice.
Also, some folks prefer to use certified cable installers—that is, professional network cable installers with
a networking industry affiliation—rather than an electrician, who might be more comfortable with A/C
power cabling than network cables.
All UTP Ethernet uses four wires: pins 1, 2, 3, and 6. Do you have to know this to troubleshoot? Only if
you want to “tone out” the cable, as illustrated in Hour 8, “Hard Basics: Guide to Being a Hardware
Geek.” In other words, if pins 4, 5, 7, and 8 have problems, it’s not a big deal.
Only NIC-to-hub cables should be straight through—that is, pin to pin. Cables that are used to connect
hubs together should be crossover. If you have a multimeter, you might want to experiment to find out
which pin on one side of the cable goes to which pin on the other side. Remember, you can do this by