[ubuntu-uk] ADSL problem

David Pashley david at davidpashley.com
Sat Dec 16 15:46:40 GMT 2006

On Dec 16, 2006 at 15:22, Dave Briggs praised the llamas by saying:
> On 16/12/06, Richard Downing <richard at langside.org.uk> wrote:
> > Is the link encrypted?  Do you need a License Registration Server
> > process running?  Did you load the driver?
> No to the first one, it was bbc.co.uk. I am using a Linksys ADSL2
> modem, connected to my ethernet, if that helps for the othr two.

I presume this is connected via an ethernet cable to your workstation
and isn't using wireless.
> > When you say 'Nothing Happens', do you mean that you just see a blank
> > page and 'done', or it there a timeout on the dns lookup?
> Blank page. Status bar says 'Connecting to...' but nothing happens. I
> have left it for quite a while without it timing out.
The first thing to do is check that your network card has been detected. 

Run "ip link"

mojo-jojo david% ip link
1: lo: <LOOPBACK,UP,10000> mtu 16436 qdisc noqueue 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:a0:c9:92:9c:c0 brd ff:ff:ff:ff:ff:ff
3: sit0: <NOARP> mtu 1480 qdisc noop 
    link/sit brd

You should see eth0. If this is the case, then your network card was
detected correctly. The next thing to do is to check that you have got
an IP address for that network device. You can do that by running "ip
addr show dev eth0"

2: eth0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:a0:c9:92:9c:c0 brd ff:ff:ff:ff:ff:ff
    inet brd scope global eth0
    inet6 2002:8b0:ed:2:2a0:c9ff:fe92:9cc0/64 scope global dynamic 
       valid_lft 2591991sec preferred_lft 604791sec
    inet6 fe80::2a0:c9ff:fe92:9cc0/64 scope link 
       valid_lft forever preferred_lft forever

The line you're interested in here is the line that starts inet. If you
don't or it starts 169.254 then you don't have an ip address assigned.

You can either get this dynamically via something called DHCP, or you
can configure it statically. We'll try dhcp first by running "sudo
dhclient eth0"

mojo-jojo david% sudo dhclient eth0
Internet Systems Consortium DHCP Client V3.0.4
Copyright 2004-2006 Internet Systems Consortium.
All rights reserved.
For info, please visit http://www.isc.org/sw/dhcp/

Listening on LPF/eth0/00:a0:c9:92:9c:c0
Sending on   LPF/eth0/00:a0:c9:92:9c:c0
Sending on   Socket/fallback
DHCPDISCOVER on eth0 to port 67 interval 4
DHCPREQUEST on eth0 to port 67
bound to -- renewal in 38436 seconds.

If you keep seeing DHCPDISCOVER lines over and over, then it means your
router is not providing addresses via DHCP, although I find this quite

If you repeat the "ip addr show eth0" line again you should see that you
now have a new "inet" line.

Lets see if our networking is working. Let's ping the machine that gave
us an IP address. If you take the IP address from the DHCPOFFER line and
try to ping it using "ping <ipaddress>". Press Ctrl-C to stop it.

mojo-jojo david% ping
PING ( 56(84) bytes of data.
64 bytes from icmp_seq=1 ttl=64 time=0.364 ms
64 bytes from icmp_seq=2 ttl=64 time=0.274 ms
64 bytes from icmp_seq=3 ttl=64 time=0.286 ms

--- ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2006ms
rtt min/avg/max/mdev = 0.274/0.308/0.364/0.039 ms

If you get lines like this, then you have working IP networking. I'll
let you work thought this email before we move onto dealing with routing
and DNS.

David Pashley
david at davidpashley.com
Nihil curo de ista tua stulta superstitione.

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