Linux adsl dialing and sharing Internet

Multiple computers access the Internet through ADSL at the same time, if there is a route, it is too simple. But what if there is no route and only a switch? There are generally two ways.

1. Use a dual network card (one connected to the internal network, one to the external network) to install the proxy server software (winGet under windows), but this method requires two network cards (waste). At the same time, it is necessary to install the agent software (annoying, and will be pirated).
2, through the shared dial-up connection to solve, this method is very simple and does not require other software.

The implementation of the second method under Windows is very simple and very simple, and will not be elaborated here.

The following is how I can make a simple record through the adsl dialing and sharing Internet under linux (tested under centOS4.4, rhel as 4, fc5), I hope to help the novice.

1, dial the number of Internet
1.1 dialing software
Linux under the dialing software a lot, but better rp-pppoe, the general Linux system will bring its own dialing software, if you Not loaded, please go to google to find one to install.
1.2 dialing settings
Switch to root user, only root can be configured.
$ su
Password:
# /sbin/adsl-setup
Follow the prompts to set the username, password, DNS, and other related information. Here is my reference configuration:
Welcome to The ADSL client setup. First, I will run some checks on
your system to make sure the PPPoE client is installed properly...

The following DSL config was found on your system:

Device: Name:
ppp0 DSLppp0

Please enter the device if you want to configure the present DSL config
(default ppp0) or enter 'n' if you want to create a new one :

LOGIN NAME

Enter your Login Name (default xyn0699647):

INTERFACE

Enter the Ethernet interface connected to the ADSL modem
For Solaris, this is likely to be something like /dev/hme0.
For Linux, it will be ethX, where 'X' is a number.
(default eth0):

Do you want The link to come up on demand, or stay up continuously?
If you want it to come up on demand, enter the idle time in seconds
after which the lin k should be dropped. If you want the link to
stay up permanently, enter 'no' (two letters, lower-case.)
NOTE: Demand-activated links do not interact well with dynamic IP
Address. You may have some problems with demand-activated links.
Enter the demand value (default no):

DNS

Please enter the IP address of your ISP's primary DNS server.
If your ISP claims that 'the server will provide dynamic DNS addresses',
enter 'server' (all lower-case) here.
If you just press enter, I will assume you know what you are
doing and not modifying your DNS setup.
Enter the DNS information here:

PASSWORD

Please enter your Password:
Please re-enter your Password:

USERCTRL

Please enter 'yes' (two letters, lower-case.) if you want to allow
normal user to start or stop DSL connection (default yes):

WIREWALLING

Please choose the firewall rules to use. Note that these rules are
very basic. You are strongly encouraged to use a More sophisticated
firewall setup; however, these will provide basic security. If you
are running any servers on your machine, you must choose 'NONE' and
set up firewalling yourself. Otherwise, the firewall rules will Deny
access to all standard servers like Web, e-mail, ftp, etc. If you
are using SSH, the rules will block outgoing SSH connections which
allocate a privileged source port.