Linux Networking Clearly Explained - lions-wing.net

CHAPTER 1 • CREATING A DIAL-UP INTERNET CONNECTION 31
If you are using an older modem that uses jumpers to
assign the COM port, you can determine the COM port
by taking a look at these jumpers. Often, the COM port
is printed on the circuit board, so you can immediately see
which COM port is in use.
Still unable to figure out which serial port your modem is
using? Check your modem’s documentation; chances are
it will tell you which serial port is enabled by default.
Resolving Serial Port Conflicts
Once you have determined which serial port your modem
requires, make sure no other device is trying to use the
serial port at the same time. Chances are your system has
only two devices that require a serial port: a serial mouse
(a mouse that connects through a serial port) and your
modem.
If you have a serial modem and a serial mouse but only
one serial port, you will need to add an additional serial
port before you can get your modem to work. But there
might be an easier solution. On the back of your computer,
look for a round PS/2 port. If you have a PS/2 port,
you can get an adapter for your serial mouse that enables
it to plug into the PS/2 port.
If your computer is equipped with two onboard serial
ports, you may need to disable one of them in order to get
your internal modem to work. Suppose your modem
wants to be connected to COM2. However, your system
is set up so that one of the onboard serial ports is connected
to COM2. To disable the onboard serial port, start
your computer and type the key (generally Delete) that
enables you to view your computer’s Setup menu. Locate
the page that contains the port settings. Disable the