The Linux PPP client lets your Linux system connect to the Internet
via a PPP server, much the same way Dial-Up Networking lets your
Microsoft Windows system do so. Behind the scenes,
wvdial calls on the services of the PPP client to
connect to a PPP server. However, it's possible to use the Linux PPP
client directly, without the aid of
wvdial. Doing
so gives you access to the many options provided by PPP, which can
prove helpful if your networking needs are too sophisticated to be met
by
wvdial's simple fire-and-forget mechanism. Even
if you're content with
wvdial, you'll benefit from
understanding the PPP client. For example, you'll find it much easier
to troubleshoot PPP problems if you understand the functions performed
by the PPP client on behalf of
wvdial.
The Linux PPP client requires several configuration
files. Rather than build these files manually, you can use
pppconfig, a program that leads you through a
dialog and then creates the proper configuration files based on your
responses. Login as
root, and issue the
command:
pppconfig
Figure 11.1 shows
pppconfig's main menu, which the program displays
whenever you start it. Notice that
pppconfig lets
you create a connection - the term by which it refers to a
complete set of configuration parameters - but it does not let you
edit an existing connection. To change a connection, you must edit the
configuration files manually. It's usually simpler to forego editing a
connection, creating a new connection instead.
To create a new connection, use the arrow keys to highlight Next
or Create, and then press
Enter.
If
pppconfig determines that the file
/etc/resolv.conf does not exist or does not
specify one or more nameservers (DNS servers), it will display the
screen shown in
Figure 11.2, which asks
you to specify nameservers. You should do so, therefore highlight Yes
and press
Enter.
Figure 11.3 shows the screen used to
specify the primary nameserver. To specify the primary nameserver,
type its IP number and press
Enter. Your ISP should be able to tell you what
IP number to specify.
You can also specify the IP number of a secondary nameserver, as
shown in
Figure 11.4. Simply type the IP
number and press
Enter. Your ISP should
be able to provide you with the IP number of the secondary namesever;
if you don't know the IP number, leave it blank.
Figure 11.5 shows the next screen
displayed by
pppconfig, which asks for a name by
which to refer to this connection. If your
/etc/resolv.conf file already specified one or
more nameservers,
pppconfig displays this screen
after its initial screen. Choose a connection name you'll be able to
recall, backspace over the default connection name, type your
connection name, and press
Enter. You
may find it convenient to use the domain name of your ISP as the
connection name.
pppconfig equivocates by sometimes referring
to a
connection, sometimes to an
ISP (Internet Service Provider), and sometimes to
a
provider. The term
connection is more accurate in this context,
because you may have several ways of connecting to a particular
ISP - for example, the ISP may have several dial-up numbers. Each
way of connecting to an ISP can be configured as a distinct
pppconfig connection.
Next,
pppconfig asks what method your ISP
uses to authenticate your access to its network, as shown in
Figure 11.6. PAP (Password Authentication
Protocol) is currently the most popular method; however, some ISPs
continue to use other methods. The technical support staff of many
ISPs cannot tell what authentication method their system uses. So, you
may have to guess; if so, initially guess PAP. If you find you cannot
establish a connection, you can try the alternative values. Select the
desired authentication method and press
Enter.
Next, you must specify your login password, as shown in
Figure 11.7. Type the password and press
Enter.
Next,
pppconfig asks you to specify some
basic connection properties. Press
Enter to exit the Configuration screen and the
Manager User Configuration screen, shown in
Figure 11.8, appears. Type the login username
assigned to you by your ISP and press
Enter. Your login username may differ from your
actual username, so be sure to use your login username.
Next, you must specify the device that corresponds to your
modem, as shown in
Figure 11.9. Type the
name of the device file, paying careful attention to capitalization,
and press
Enter.
The program next asks whether you want it to establish a default
route when it makes a connection, as shown in
Figure 11.10. You almost certainly do, so accept
the default choice - Enable Default Route - by using the arrow
keys to highlight Ok and pressing
Enter.
Figure 11.11 shows the next
pppconfig screen, which requests information on your
computer's network address (IP number). Most ISPs assign your computer
a different network address each time you establish a connection. Some
ISPs give you the option of having a static network address, meaning
that your computer's network address is always the same.
Unless your ISP has assigned your computer a static network
address, simply press
Enter. If your
computer has a single static network address, type the address
followed by a colon and press
Enter. If
it has separate local and remote network addresses, type the local
address, a colon, and the remote address; then press
Enter.
Next, you must specify your modem's speed, as shown in
Figure 11.12. This refers to the speed of the
connection between your modem and your system, not to the speed of the
connection between your modem and your ISP, which is normally a
smaller value. Unless you have a particular reason for doing
otherwise, you should accept the default speed of 115200 by pressing
Enter.
Next, as shown in
Figure 11.13,
pppconfig lets you specify a modem initialization
string, which it will send to the modem before establishing a
connection. Simply press
Enter to
accept the default initialization string, which works correctly for
most modems and situations.
Next, as shown in
Figure 11.14, you
must specify the number your modem should dial to reach your ISP. Type
the number without spaces or punctuation. With the number, include any
necessary prefix or suffix digits just as you would dial them
yourself - for example, the
1 and area code
needed to access a long distance number.
Next, as shown in
Figure 11.15, you
must specify whether your phone line accepts tone dialing or pulse
dialing. Most U.S. phone lines accept tone dialing; unless you're
certain your line does not, specify tone dialing, highlight Ok, and
press
Enter.
Next,
pppconfig gives you the opportunity to
review and change your entries. Press
Enter to exit the Properties screen.
Figure 11.16 shows the screen that appears. To
view or change an entry, highlight the entry and press
Enter. When you're satisfied that your entries
are correct, highlight Finished and press
Enter.
pppconfig writes the PPP configuration files
according to your specifications. Press
Enter to exit the Finished screen. Unless you
want to specify another connection, highlight Quit and press
Enter to exit the main menu.
Finally, you're ready to establish a PPP connection. While
logged in as
root, issue the following
command:
pon
connection
Where
connection is the connection
name you earlier specified in
pppconfig.
You can monitor the progress of the operation by issuing the
following command in a separate virtual console:
tail -f /var/log/messages
This command continually displays messages as they're posted to
the system log file. Because PPP writes log entries that describe its
progress, the command lets you see what PPP is doing. When you're done
viewing log entries, type
Ctrl-C to exit the
tail command.
You can see even more detail by using the command:
tail -f /var/log/ppp.log
You can verify that the PPP connection has been established by
issuing the following command:
ifconfig
If the output of the command includes a description of a PPP
connection, the connection was successfully established. To verify
that the connection is operational, issue the
ping
command:
ping www.oreilly.com
To terminate the connection, type the command:
poff
If your connection failed, you should check the following before
contacting your ISP or other Linux users for support:
-
Did you correctly specify your ISP's phone number?
-
Did you correctly specify your userid and password?
-
Did you correctly specify your modem's device file and line speed?
-
Is your modem properly connected to your telephone line?
-
Is your telephone line operational?
When you want to terminate the PPP connection, you can click on the Disconnect button of the dialog box you used to establish the connection.
