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Old 07-31-2010, 08:27 AM   #1
Joe Soap
Registered: Sep 2001
Location: Switzerland
Distribution: Debian, Sidux
Posts: 225

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Internet/network connection gone awol

I have Debian testing installed on two PCs and, since an unplanned reboot (initiated by my daughter) yesterday, the network connection on the one PC no longer works.

All pings return "Network is unreachable".

I changed the network cable with one that is definitely working and the cable is not the problem.

I rebooted with Ubuntu live and there was no problem with the network connection.

My conclusion is that some setting or configuration has gone wrong on this pc, but I have no idea where to start investigating. If anybody can point me in the right direction I'd be most grateful.

I guess the basic question here is: what should be running to ensure that the network is working ...


Last edited by Joe Soap; 07-31-2010 at 09:01 AM. Reason: calrification
Old 07-31-2010, 09:44 AM   #2
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ifconfig -v
That command lists what interfaces are up. There should be
lo #Yell if you don't see this!
eth0 # should show 'inet address' if you have one, and hardware interrupt.

If that lot looks ok, post the output of 'cat /etc/resolv.conf'

Other useful commands are netstat, route. BTW, we haven't a breeze about your network, so to be more precise, we have to be told. Are you logging on to some dhcp router?
Old 07-31-2010, 12:01 PM   #3
Joe Soap
Registered: Sep 2001
Location: Switzerland
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Thanks for the answer business kid.

Here's the output of ifconfig -v
lo        Link encap:Local Loopback  
          inet addr:  Mask:
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:160 errors:0 dropped:0 overruns:0 frame:0
          TX packets:160 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:14024 (13.6 KiB)  TX bytes:14024 (13.6 KiB)
eth0 doesn't show up at all.

cat /etc/resolv.conf shows this:
For what it's worth, I can't ping

Here are the first few lines of netstat:
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State      
Active UNIX domain sockets (w/o servers)
Proto RefCnt Flags       Type       State         I-Node   Path
unix  11     [ ]         DGRAM                    4681     /dev/log
unix  2      [ ]         DGRAM                    2109     @/org/kernel/udev/udevd
unix  2      [ ]         DGRAM                    4965     @/org/freedesktop/hal/udev_event
unix  3      [ ]         STREAM     CONNECTED     27242    @/var/run/hald/dbus-UDyPH1dXP3
unix  3      [ ]         STREAM     CONNECTED     27241    
unix  3      [ ]         STREAM     CONNECTED     27239    /var/run/dbus/system_bus_socket
unix  3      [ ]         STREAM     CONNECTED     27238    
unix  3      [ ]         STREAM     CONNECTED     27067    /var/run/dbus/system_bus_socket
unix  3      [ ]         STREAM     CONNECTED     27066    
unix  3      [ ]         STREAM     CONNECTED     22282    /var/run/dbus/system_bus_socket
unix  3      [ ]         STREAM     CONNECTED     22281    
unix  3      [ ]         STREAM     CONNECTED     22220    @/tmp/.X11-unix/X0
unix  3      [ ]         STREAM     CONNECTED     22219    
unix  3      [ ]         STREAM     CONNECTED     22218    /tmp/orbit-alpha/linc-deb-0-1545cdcdbe0c6
unix  3      [ ]         STREAM     CONNECTED     22217    
unix  3      [ ]         STREAM     CONNECTED     22214    /tmp/orbit-alpha/linc-8a8-0-2960170b2aeca
unix  3      [ ]         STREAM     CONNECTED     22213    
unix  3      [ ]         STREAM     CONNECTED     22208    @/tmp/dbus-JjzIJbUKx2
My network is a home lan. I've got an adsl modem connected to a netgear switch and 3 PCs connected to the switch. I didn't do anything to set it up or configure it - after I installed the OS everything worked. Two of the PCs run Debian testing and the other one runs sidux.

Hope that helps. Let me know what other info I should supply.

Old 07-31-2010, 11:52 PM   #4
Registered: Nov 2005
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try "ifconfig -a". That will show all interfaces even those not up. The fact that eth0 is not shown with ifconfig shows that the eth0 interface is down. If ifconfig -a shows eth0, you can type "ifup eth0" to bring it back up with startup interface settings or yu can manually set them with, for example, "ifconfig eth0 netmask broadcast"

If ifconfig -a doesn't show eth0 (or eth1 eth2 or whatever) you have a problem with the OS recognising the interface. In this case you should start with lsmod to check loaded drivers, make sure the NIC is seated correctly, perhaps try another NIC if you have one
Old 08-01-2010, 03:05 AM   #5
Joe Soap
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Thanks themanwhowas.

"ifconfig -a" shows eth0 but "ifup eth0" just says "interface already configured".

I did the manual thing as you suggested:
ifconfig eth0 netmask broadcast
but with the netmask and broadcast slightly changed to correspond with what I see when I type "ifconfig" on my other PC:
ifconfig eth0 netmask broadcast
After this it was possible to connect to the modem ( but I still cannot get on the internet ("unable to connect", according to Firefox) and when I reboot, eth0 is still down, so I have to start it manually.

Any help to sort out these last two problems will be highly appreciated.


Last edited by Joe Soap; 08-01-2010 at 03:13 AM. Reason: correction
Old 08-01-2010, 09:36 AM   #6
Joe Soap
Registered: Sep 2001
Location: Switzerland
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Solved, sort of. I gave up and reinstalled. It works, obviously, but I don't know how or why ....
Old 08-01-2010, 09:58 AM   #7
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I had something similar last week. My desktops NIC was
non-functional even after booting into windows. I shut down the computer for a few minutes and rebooted into openSuSE. The device was working again.


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