3.2. Testing Adapters
While most problems with adapters,
such as Ethernet cards, are configuration errors, sometimes adapters
do fail. Without getting into the actual electronics, there are
generally three simple tests you can make with adapters. However,
each has its drawbacks:
-
If you have some doubts about whether the
problem is in the adapter or network, you might try eliminating the
bulk of the network from your tests. The easiest approach is to
create a two-computer network using another working computer. If you
use coaxial cable, simply run a cable known to be good between the
computers and terminate each end appropriately. For twisted pair, use
a crossover cable, i.e., a patch cable with send and receive crossed.
If all is well, the computers should be able to communicate. If they
don't, you should have a pretty clear idea of where to look
next.
The crossover cable approach is analogous
to setting up a serial connection using a null modem. You may want to
first try this method with two working computers just to verify you
are using the right kind of cable. You should also be sure IP numbers
and masks are set appropriately on each computer. Clearly, the
drawbacks with this approach are shuffling computers around and
finding the right cable. But if you have a portable computer
available, the shuffling isn't too difficult.
-
A second alternative is
to use the configuration and test software provided by the
adapter's manufacturer. If you bought the adapter as a separate
purchase, you probably already have this software. If your adapter
came with your computer, you may have to go to the
manufacturer's web page and download the software. This
approach can be helpful, particularly with configuration errors. For
example, a combination adapter might be configured for coaxial cable
while you are trying to use it with twisted pair. You may be able to
change interrupts, DMA channels, memory locations, bus mastering
configuration, and framing types with this software.
Using
diagnostic software has a couple of limitations. First, the software
may not check for some problems and may seemingly absolve a faulty
card. Second, the software may not be compatible with the operating
system you are using. This is particularly likely if you are using
something like Linux or FreeBSD on an Intel platform.
-
The
third alternative is to swap the card for one that is known to work.
This presumes that you have a spare card or are willing to remove one
from another machine. It also presumes that you aren't having
problems that may damage some other component in the computer or the
new card. Even though I generally keep spare cards on hand, I usually
leave this test until last whenever possible.
 |  |  |
| 3. Connectivity Testing |  | 3.3. Software Testing with ping |
