ADSL and Linux

The most popular and accessible broadband service in Australia is ADSL, which uses an ordinary telephone line to deliver high-speed Internet access. In this column, we’ll look at connecting a Linux computer to an ADSL connection using both Bridged Ethernet and PPPoE- based connections.

Essential details

After you sign up to an ADSL service, your ISP will supply you with connection information. Depending on the type of ADSL connection, this information will include some of the following: connection method, username and password, gateway IP, customer IP, subnet mask and DNS servers for your ISP. Keep this information handy when setting up your connection, as you will need to refer to it.

Modems and routers

Connecting to an ADSL service requires either a modem or a router. Both perform the same function in connecting to your ISP, but the configuration required on your computer is different.

The first thing to look for when choosing an ADSL modem/router is Ethernet support. Many ADSL modems/routers are designed for USB. Ethernet support will require you to install an Ethernet card in your computer, but this will save a lot of hassles in finding drivers for a USB device.

An ADSL modem requires you to have some software on your computer with which perform the connection to your ISP. This article concentrates mostly on ADSL modems because they require the most configuration under Linux. The information supplied to you by your ISP will indicate if you have a modem or a router; if you have a modem, skip to the next section on PPPoE connections.

If you own an ADSL router, setting it up to work with Linux is easy. First, configure your router according to your ISP’s instructions. You can access the router with a Web browser such as Mozilla. Be sure to enable the DHCP, NAT and firewall features of your router. Next, open a shell in Linux and check to see if the program /sbin/dhclient exists. If it does not, install the DHCP package included on this month’s cover CD. To connect Linux to your router, become the super user with the ‘su’ command in the shell and type the following:

$ /sbin/dhclient

PPPoE connections

PPPoE (Point-to-Point Protocol over Ethernet) is the most common method used in Australia to connect over ADSL. ISPs including Big Pond, iiNet and Internode all use PPPoE. To connect using PPPoE with a modem you will need to install a login client (See here for a screenshot). We have included a copy of the Roaring Penguin PPPoE client ( on the PC World September 2003 cover CD. To install the Roaring Penguin, untar the archive on your hard disk, change to the newly created directory, change to the super user using the ‘su’ command, and type the following in a shell:

$ ./go-gui

This will compile, install and run the Roaring Penguin for the first time. In future you can access the GUI by typing:

$ tkpppoe

Configuring the Roaring Penguin is reasonably self-explanatory, just enter all of the details supplied to you by your ISP in the locations provided. In most cases, the Ethernet card to which your modem is connected will be the default setting of ‘eth0’, but if you have more than one Ethernet card installed it may be ‘eth1’. After entering your settings, click the OK button to save the connection information.

You can now connect to your ISP by selecting the connection from the list and clicking the Start button. If you encounter problems when connecting, compare the settings entered to those provided by your ISP and retry connecting.

Bridged Ethernet connections

Some smaller ISPs now offer Bridged Ethernet as a method of connecting to their service, often in conjunction with ADSL services that include a static IP.

The first installation step is to configure your modem according to your ISP’s instructions. Once your modem is configured, open a shell and change to the super user using the ‘su’ command. If your ISP instructions mention DHCP, install the DHCP package included on this month’s cover CD, and type the following command to set up your ADSL connection:

$ /sbin/dhclient

If, instead, your ISP supplies you with a static IP and a gateway, type the following commands:

$ /sbin/ifconfig eth0 [static ip] netmask [netmask]
$ /sbin/route add default gw [gateway]

To complete the configuration, open /etc/resolv.conf in a text editor and add your ISP-supplied DNS server addresses as follows:

nameserver [primary IP]
nameserver [secondary IP]

For additional information on connecting to ADSL with Linux, visit or

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Alastair Cousins

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