Broadband - setting up an ethernet ADSL modem/router

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Chris Lale
chrislale AT users DOT berlios DOT de

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Revision History


Revision 0.1 11th March 2006 Revised by Chris Lale
Initial release.

Revision 0.2 27th November 2007 Revised by Chris Lale
Reformatted for newbiedoc package. Added Revision History, Abstract and Licence notice in appendix.


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Abstract

This document is for getting an ethernet ADSL modem/router working on a Debian system. Not for a USB ADSL modem.


Contents


1 Connecting the ASDL modem/router

These instructions are for an ethernet ADSL modem/router, not a USB ADSL modem.

Assume router without DHCP (which dynamically allocates your PC an address on the network if it does not have one). You can enable Your router's DHCP server later, if it has one.

Connect router's ADSL socket to telephone socket (via microfilter usually). Connect router's ethernet port to PC's ethernet socket using cat 5 cable.


2 Configuring the ethernet interface

Without DHCP, you have to give your PC an IP address on the router's network.

Your PC must be running on the same network as your router. This network is set by default by the router manufacturer, but you can change it later. The network is usually one of the private networks in the range 192.168.nnn.0 with netmask 255.255.255.0. (The netmask means that the first three address numbers are fixed, but the fourth number can have any value.) To find the network, look in the router's documentation for the router's IP address. It is usually the first address in the network eg 192.168.nnn.1. Since the router is going to be your gateway to the internet, this will also be your PC's gateway address.

In this example, the router's address is 192.168.1.1. This means that the address representing the whole network is 192.168.1.0, and the broadcast address is 192.168.1.255. (The router sometimes needs to send packets of information to all devices on the network, so every device must have this broadcast address in its configuration.) You can choose an address for your PC from the remaining addresses in the range. In this example, the PC's ethernet card is configured to use address 192.168.1.2.

The configuration of your PC's ethernet card(s) is held in the file /etc/network/interfaces. If you have only one ethernet card (eth0) the file will contain two entries - one for the loopback device (lo) and one for the ethernet card (eth0). Edit the file as root and add/modify the address (192.168.1.2), netmask (255.255.255.0), network (192.168.1.0), broadcast(192.168.1.255) and gateway (192.168.1.1) addresses. You can use Nano from a terminal or terminal window to do this.

$ su
Password:
# nano /etc/network/interfaces
 
...

# exit
$

The resulting /etc/network/interfaces file should look something like this:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet static
	address 192.168.1.2
	netmask 255.255.255.0
	network 192.168.1.0
	broadcast 192.168.1.255
	gateway 192.168.1.1
	# dns-* options are implemented by the resolvconf package, if installed
	dns-nameservers nnn.nnn.nnn.nnn nnn.nnn.nnn.nnn
	dns-search home
	name Ethernet LAN card

3 Configuring the PC's hostname

3.1 Check the PC's hostname

Check your PC's hostname with fully qualified domain name switch

$ hostname --fqdn
sempron.home

If you get localhost.localdomain or a hostname but no domain name, use the alias switch to find out if there is a named domain.

$ hostname --alias
localhost  sempron  sempron.home

In this example the hostname is sempron, the domain name is home and the fully-qualified domain name is sempron.home. You may not have a domain name if you did not enter one when you installed Debian.

3.2 edit /etc/hosts

You can use Nano from a terminal or terminal window to do this.

$ su
Password:
# nano /etc/hosts
 
...

# exit
$

Add the IP address for your PC if it is not present (and remove other references from eg first line). Include the hostname aliases.

The /etc/hosts file should look something like this:

192.168.1.2 sempron.home sempron
127.0.0.1 localhost.localdomain localhost

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts

4 Configure nameservers

Your broadband supplier may provide you with the IP addresses of its DNS servers. These are used by your router to convert domain names like 'google.co.uk' into IP addresses like 216.239.57.104. As root, modify the file /etc/resolv.conf with these addresses. It should look something like this:

nameserver nnn.nnn.nnn.nnn
nameserver nnn.nnn.nnn.nnn
search home

5 Connect your PC to the router's network

Bring up the eth0 interface with the new configuration by restarting the networking service. Do this as root.

# /etc/init.d/networking restart

6 Checking the network

Power up the router. You can check that your PC can communicate with the router using Ping.

$ ping -c3 192.168.1.1
PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=0.388 ms
64 bytes from 192.168.1.1: icmp_seq=2 ttl=64 time=0.384 ms
64 bytes from 192.168.1.1: icmp_seq=3 ttl=64 time=0.384 ms

--- 192.168.1.1 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 1999ms
rtt min/avg/max/mdev = 0.384/0.385/0.388/0.016 ms

If you get an error like

From 192.168.1.2 icmp_seq=1 Destination Host Unreachable

go back and check your documentation for the router's address.

7 Configuring the router

Open a browser and enter the router's address in the location bar.

http://192.168.1.1

Follow your router's setup instructions and configure the router with the settings, username and password from your broadband provider.

Save the settings. The router should reboot automatically.

If you may have leds on the front of the router. You should see this sequence:

  1. Power
  2. ASDL - physical connection made
  3. Online - username and password accepted.

See your router's documentation for particular details.

8 Check that you can connect to the internet

8.1 Check that the router is working

$ ping -c3 216.239.57.104

8.2 Check that DNS is working

$ ping -c3 google.co.uk

8.3 Check that your browser works

Visit

http://google.co.uk

9 Appendix A: Licence

Copyright (c) 2006-2007 Chris Lale, chrislale AT users DOT berlios DOT de

GNU FDL Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License."

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Content is available under GNU Free Documentation License 1.2, unless otherwise stated.