6. Configuring The Network

The configuration file

After you have installed knoppix to your hard disk, the network autodetection has been disabled. This is because we chose to install a debian style system. So, now we will need to do the configuration manually.

The configuration file that is controlling how the network is handled is /etc/network/interfaces, so we are going to edit this file. This is how the file should look like in our setup of the box with two network cards.

# /etc/network/interfaces -- configuration file for ifup(8), ifdown(8)

# The loopback interface
# automatically added when upgrading
auto lo eth0 eth1
iface lo inet loopback
iface eth1 inet static
        address 192.168.1.1
        netmask 255.255.255.0
iface eth0 inet dhcp

This file is saying we have automatically configured interfaces for loopback (lo), eth0 and eth1 interfaces. loopback is a virtual network interface, used by some programs to connect to the local computer. Hence it's name. eth0 and eth1 are the real network interfaces in your computer. eth1 is the one we will assume is connected to your local network and eth0 is the one that will be connected to the internet. This choice is rather arbitrary and could be vice versa, but we will for the rest of this document assume you have configured everything like this.

The interface eth1 is configured as a static network interface, which means it will never change it's ip address. You are allowed to choose an ip address here, since it will not be used anywhere else but on your local network, but for safety reasons it is best if you use an address in one of the reserved ranges, which are listed below.

The interface eth0 is configured as a dhcp client interface, which may not be appropriate for your configuration, since it is dependent of the upstream Internet Service Provider, and mine delivers dhcp addresses. Other options usually are dialup kinds and network configuration there is different. However, sometimes you can buy routers that dial up for you and provide you a dhcp address anyway, so in case you have one like this, this configuration may be still valid in your situation. If not, you are at the moment, on your own. Sorry, but I have to limit the scope for now ;-)

Verifying the network interface configuration

Afterwards, we can test the configuration by typing the following set of commands:

kristof@knoppixbox:~/$ ifup eth0
kristof@knoppixbox:~/$ ifup eth1
kristof@knoppixbox:~/$ ifconfig
eth0      Link encap:Ethernet  HWaddr 52:54:05:C3:FF:0E  
          inet addr:10.0.1.3  Bcast:255.255.255.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:40495 errors:0 dropped:107 overruns:0 frame:12
          TX packets:30324 errors:0 dropped:0 overruns:0 carrier:0
          collisions:1338 txqueuelen:100 
          RX bytes:21385539 (20.3 MiB)  TX bytes:4947621 (4.7 MiB)
          Interrupt:12 Base address:0xc000 

eth1      Link encap:Ethernet  HWaddr 00:D0:09:5F:7E:83  
          inet addr:192.168.1.1  Bcast:192.168.1.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:13509602 errors:301 dropped:16108 overruns:261 frame:0
          TX packets:12756299 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100 
          RX bytes:783185984 (746.9 MiB)  TX bytes:3534492144 (3.2 GiB)
          Interrupt:11 Base address:0x5000 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:2171 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2171 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:12300096 (11.7 MiB)  TX bytes:12300096 (11.7 MiB)

This could be enough to get you going if your ISP gives you a name server via dhcp, but some don't. Then you need to additionally add your nameserver into the nameserver configuration file, /etc/resolv.conf, so that it contains the single line nameserver 195.130.132.17 or whatever ip address your ISP provides you with. The command to do this is sudo nedit /etc/resolv.conf. There will be more details about this in the dns section, but you need to get your network going at this stage in order to install some of the tools we'll need in the following sections.

Proxy Servers

Some providers want all traffic to go through their proxy servers, in order to provide some "content caching". Of course, in the mean time it is easier for them to watch what you are doing, but anyway.

When you need to set a proxy server, you have to influence the environment variable that most tools look at. What you need to do is execute the following command.

Code listing 6.3: Setting a proxy server

Substitute your proxy server in this command kristof@knoppixbox:~/$ export set http_proxy="http://proxy.servers.com:8080/" kristof@knoppixbox:~/$ echo $http_proxy http://proxy.pandora.be:8080/

Of course, setting this all the time becomes a nuisance in no time, so we should be able to set it in one place. What you can do is add this command to the end of the file /etc/profile and you should get the same effect without every time issuing the command.

Troubleshooting

Again, I hate to admit it, but sometimes things go wrong. Generally, it is not a problem to fix it. What you need to figure out is the source of the problem and this requires a little networking knowledge. However, some things are easy verifiable, and a small checklist is provided here:

• Check if all network interfaces are up, using ifconfig. If they are up, you can start pinging. In case you got an ip address via a DHCP server, you can be happy with that part already, you got an IP address and the connection to your upstream provider is probably ok.
• Can you connect to your upstream provider? You can first start pinging IP addresses of server like your name server. If this ping is ok, you can assume the network is ok. Is your nameserver filled in in /etc/resolv.conf, like it should be? Then you can try and ping your nameserver, or any other address that responds to ping (most websites addresses do), to check if the name resolution works.

Code listing 4: successful ping to name server

kristof@knoppixbox:~# cat /etc/resolv.conf nameserver 195.130.130.130 nameserver 195.130.131.2 search pandora.be kristof@knoppixbox:~# ping -c 5 195.130.131.2 PING 195.130.131.2 (195.130.131.2): 56 data bytes 64 bytes from 195.130.131.2: icmp_seq=0 ttl=60 time=13.3 ms 64 bytes from 195.130.131.2: icmp_seq=1 ttl=60 time=18.4 ms 64 bytes from 195.130.131.2: icmp_seq=2 ttl=60 time=18.3 ms 64 bytes from 195.130.131.2: icmp_seq=3 ttl=60 time=17.3 ms 64 bytes from 195.130.131.2: icmp_seq=4 ttl=60 time=15.4 ms --- 195.130.131.2 ping statistics --- 5 packets transmitted, 5 packets received, 0% packet loss round-trip min/avg/max = 13.3/16.5/18.4 ms kristof@knoppixbox:~#

• If you got this far, you should be able to surf the internet. Take Konquerer for a spin and check it out. While you're at it, maybe something new is on on slashdot? If you can't get there, don't forget some providers have a proxy server to be configured in the browser, and not all browsers pick up the environment variable.