lost internet connectivity: need help troubleshooting

[tomcloyd]

I have an always-on broadband connection via a cable modem. My laptop, on which I'm typing this, connects to the WWW just fine, using this - via a usb cable. Some time this afternoon, while flailing around trying to connect my laptop to my desktop for shared file access, I lost internet access on my desktop. I've tried everything I can imagine - power downs, different usb ports, reboots, intense exploration of system settings. Nothing makes any difference. I have connectivity with the laptop; I don't with the desktop.

I don't know what to do next. At one point on the desktop, I did install the "wicd" program (via Synaptic), thinking it might help me with my ethernet connection problem. I fiddled a bit with its settings, but didn't seen anything promising, and didn't understand much of it. I may have fouled something up while doing this, but don't know enough to find out what.

How do I troubleshoot this problem? I really need to get internet connectivity back with this machine - my main work computer. I'm thinking there must be some config file somewhere that's messed up, but have no idea where to go with this idea.

I'm open to all suggestions!

t.

[Ole Juul]

Re: lost internet connectivity: need help troubleshooting

You mention three kinds of connection:
1/ cable
2/ USB
3/ ethernet
I'm not clear about the configuration. Is your laptop now plugged into your cable modem using a USB connection? Where does the ethernet part come into the picture?

[Snowhog]

Re: lost internet connectivity: need help troubleshooting

On the desktop PC, cat your /etc/network/interfaces file:

cat /etc/network/interfaces

Note the output and type it exactly as it appears in your reply.

[tomcloyd]

Re: lost internet connectivity: need help troubleshooting

Here is my CLI dialog:

$ cat /etc/network/interfaces
auto lo
iface lo inet loopback

$

Thanks for your help.

t.

[Snowhog]

Re: lost internet connectivity: need help troubleshooting

Assuming that your Ethernet device in the desktop is reported as eth0, edit your /etc/network/interfaces file (as root) and add the following two lines to the end:

auto eth0
iface eth0 inet dhcp

so your file looks like:

auto lo
iface lo inet loopback
auto eth0
iface eth0 inet dhcp

Save and close.

Open a console (if not already in one) and type:

sudo ifconfig eth0 down
sudo ifconfig eth0 up

If the iface is correct (eth0), you should have network connectivity back.

[tomcloyd]

Re: lost internet connectivity: need help troubleshooting

Sorry to be so ignorant, but...

"Assuming that your Ethernet device in the desktop is reported as eth0, ..."

reported WHERE? I find this baffling, but when I plug my cable modem's USB cable into its socket on my netbook, I get a nice little popup which tells me that it's detected 'eth1" - this is coming from a Network Management widget I THINK I installed - and which isn't even available on my desktop ((!). When I plug the same cable into my desktop a great silence is heard throughout the universe.

So how do I get the same info. reported on my desktop? Any reason to expect that it'd be the same? I've tried to find a spiffy linux command to report such info from the CLI and have not succeeded.

Cluelessly yours,

t.

[Snowhog]

Re: lost internet connectivity: need help troubleshooting

Sorry to be so ignorant, but...

So how do I get the same info. reported on my desktop?

On the desktop, open a console and type:

sudo ifconfig | grep Ethernet

You'll get output similar to this (from my system):

eth0 Link encap:Ethernet HWaddr 00:16:36:dc:79:d7
wlan0 Link encap:Ethernet HWaddr 00:16:e3:aa:4c:ac

The top line contains the identification of my wired ethernet hardware device.

[tomcloyd]

Re: lost internet connectivity: need help troubleshooting

Hmm. Didn't work. I very carefully followed your instructions, after determining that I was dealing with eth0 on my desktop. My interfaces file is the same as you instructed. I did the sudo ifconfig... stuff afterwards. No connectivity, even after reboot. I'm using the same usb cable now to send this post, so the cable and modem are fine - on my netbook.

One thought - when I did the '...grep Ethernet' thing, I got this

eth0 Link encap:Ethernet HWaddr 00:11:85:68:26:50
eth0:avahi Link encap:Ethernet HWaddr 00:11:85:68:26:50

Is that second line of any value? Should I do something different?

t.