PPPoE has become much more important recently, as it is the connection method of choice by a number of DSL providers. Fortunately for Linux users, a number of functional options are available, most of which are easily configurable. PPPoE is nothing new; it is simply the same PPP as used over dial-up, except it is used over Ethernet.
For the purposes of this section, we'll assume that your DSL modem and equipment are properly configured and ready for use. More information on how this is accomplished can be found in the excellent Linux DSL HOWTO, written by David Fannin and Hal Burgiss (http://www.tldp.org/HOWTO/DSL-HOWTO). Additionally, we'll assume that the Ethernet card in your PC is installed and operational.
In most DSL environments the DSL modem is configured to be a bridge, meaning that it won't have an IP address. As a result of this, your server will be configured with a WAN IP address. Before enabling the WAN interface, you should make certain that you've patched all of the listening services on your machine. Additionally, you should consider using an IPtables or other firewall. Security when connecting directly to the Internet should be of the utmost importance. It has been reported that unpatched versions of some Linux distributions survive only a few hours on the Internet before they're compromised. Make sure you've done as much as possible to ensure that this doesn't happen to you!
To get started with configuring PPPoE, you will need to obtain a PPPoE client. There are a number of clients available, including one from Roaring Penguin that has become very popular with many users and providers. It can be downloaded from http://www.roaringpenguin.com in both source format and as pre-compiled RPMs. When you've downloaded and compiled or installed the software, you are ready for configuration. The client software comes with a very easy to use configuration script called adsl-setup. It will ask you a number of questions about your system, network, and PPPoE user information. In some cases it will have already provided the answers, requiring you to only confirm!
However helpful, the script isn't foolproof, so we'll walk through a manual configuration. It's also a good idea, especially from the network administrator's viewpoint, to have a good idea of how software is configured, just in case something goes wrong in the future.
Configuring the client is pretty easy, especially if you've previously set up a standard PPP configuration. First, you'll need to edit the /etc/ppp/pap-secrets file. You will need to replace the default values with your PPPoE username and password. The file will look something like this:
#User #Server #Password #IP groucho@dslcompany.to * my_password *
Next, open the /etc/ppp/pppoe.conf file in your text editor. You will need to tell it both your WAN interface name, and your PPPoE username. The relevant lines in the file appear as follows:
# Ethernet card connected to ADSL modem ETH=eth0 # ADSL user name. You may have to supply "@provider.com" USER=groucho@dslcompany.to
The file contains a number of additional configuration options. Unless you're really certain that you need to change these, you probably shouldn't. If you are determined to make some changes, refer to the PPP manpages for more information.
Lastly, if you haven't already configured your DNS servers in the /etc/resolv.conf file, this should be done now. Detailed information about DNS configuration can be found in Chapter 5.
When you've finished with the configuration, you can now test the connection to see if it works. The adsl-start script is used specifically for this purpose. You can call it from the command line, or, ideally, include it in your system startup scripts. This is accomplished differently for almost every distribution. Consult documentation specific to your distribution for specifics on how to install startup scripts.
If the startup script completes without errors, you should be connected to the Internet. A quick and easy way to test this is to ping something that will answer. Success will look like this:
vlager# ping www.google.com PING www.google.akadns.net (66.102.7.99) 56(84) bytes of data. 64 bytes from 66.102.7.99: icmp_seq=1 ttl=245 time=5.94 ms 64 bytes from 66.102.7.99: icmp_seq=2 ttl=245 time=5.02 ms 64 bytes from 66.102.7.99: icmp_seq=3 ttl=245 time=5.02 ms ctrl-c --- www.google.akadns.net ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2009ms rtt min/avg/max/mdev = 5.028/5.333/5.945/0.440 ms vlager#
Additionally, you can check the configuration by using ifconfig:
vlager# ifconfig -a
eth0 Link encap:Ethernet HWaddr 00:08:02:F0:BB:0E
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:8701578 errors:6090 dropped:0 overruns:0 frame:5916
TX packets:3888596 errors:0 dropped:0 overruns:0 carrier:0
collisions:6289 txqueuelen:100
RX bytes:1941625928 (1851.6 Mb) TX bytes:1481305134 (1412.6 Mb)
Interrupt:30
eth1 Link encap:Ethernet HWaddr 00:90:27:FE:02:A0
inet addr:10.10.0.254 Bcast:10.10.0.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:48920435 errors:0 dropped:0 overruns:0 frame:0
TX packets:55211769 errors:0 dropped:0 overruns:2 carrier:9
collisions:367030 txqueuelen:100
RX bytes:2018181326 (1924.6 Mb) TX bytes:1564406617 (1491.9 Mb)
Interrupt:10 Base address:0x4000
.
ppp0 Link encap:Point-to-Point Protocol
inet addr: 64.168.44.33 P-t-P:64.168.44.1 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1492 Metric:1
RX packets: 8701576 errors:0 dropped:0 overruns:0 frame:0
TX packets: 3888594 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:10If something isn't working properly at this point, check all of your connections, and ensure the DSL gear is properly configured. Additionally, recheck your username and password in the configuration filesa mistyped password is one of the most common configuration problems!