[oclug] Eth0 dead after Ubuntu update

[Stephen Gregory]

On Thu, Sep 30, 2010 at 10:35:33PM -0400, Aaron Wilcox wrote:
> > eth0      Link encap:Ethernet  HWaddr 00:1f:d0:af:30:27  
> >           UP BROADCAST MULTICAST  MTU:1500  Metric:1

The UP keyword means that the software side of the the ethernet device
is on and ready to accept packets. To see the hardware side use the mii-tool:

$ sudo mii-tool eth0

The output should be something like:
    eth0: negotiated 100baseTx-FD, link ok
or
    eth0: no link
If you get the second message then there is something wrong with the
device. The cable could be loose.

For better debug information have a look at the output of
$ dmesg
with is also in /var/log/kern.log

If the link is ok then network-manager may be failing. you could try
running dhcp manually:

$ sudo dhclient eth0

> > Sep 30 22:04:19 thoth NetworkManager: <info>  (eth0): bringing up device.
> > Sep 30 22:04:19 thoth NetworkManager: <info>  (eth0): preparing device.
> > Sep 30 22:04:19 thoth NetworkManager: <info>  (eth0): deactivating device (reason: 2).

I would love to know what "reason 2" is.



-- 
sg