DHCP setup problems

[dsr at tao.merseine.nu]

On Mon, May 01, 2006 at 09:32:11PM -0400, Doug wrote:
> That worked for my Linux box.  I did not change a setting, and the box
> was able to get on the Internet with no changes.  I tried to connect
> both my Linux (Ubuntu) laptop, and an IMac, but neither one worked. 
> Both the laptop and the IMac had been using wireless to connect, but
> cannot do so now (I am not sure if that messes things up).
> 
> I thought the Linux box would need 2 things to be setup.  I set the
> /etc/resolv.conf to be exactly like the one on the box that works:
> search comcast.net
> nameserver 68.87.71.226
> nameserver 68.87.73.242

The "search comcast.net" line only works for one thing: if you
type a hostname without a full domain, it will try
hostname.comcast.net before failing.

> /etc/network/interfaces    has a line
> iface eth0 inet dhcp
> 
> I made sure that line was "live" by switching the cable between my big
> box and the laptop.  If I do sudo ifdown eth0; sudo ifup eth0, the
> computer tries 6 times, but fails.  There are two clues in the output.
> First it complains that there is alread a pid file
> /var/run/dhclient.eth0.pid with pid 1.  Second, the failed lines look
> like this:
> 
> DHCPDISCOVER on eh0 to 255.255.255.255.255 port 67 interval 7
> 
> For a moment, I thought the 4 255 was suspicious, but I just checked
> on the working machine, and ifup does the same thing, except it gets a
> DHCPOFFER, and then it works.
> 
> So I am not sure where to trouble shoot next.  Is wireless failing an
> issue? Are there other settings to change?

Your wireless is probably not working well. Try this:

iwconfig eth0

You should get back something like this:

eth0      IEEE 802.11b  ESSID:"bearsong"  
          Mode:Managed  Frequency:2.462 GHz  Access Point: 00:09:5B:6A:59:C4   
          Bit Rate=11 Mb/s   Tx-Power=20 dBm   
          Retry limit:7   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:on
          Link Quality=68/100  Signal level=-59 dBm  Noise level=-83 dBm
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:1

If you don't, then your wireless card hasn't found your access
point. Try setting:

ifdown eth0
iwconfig eth0 essid any
ifup eth0

-dsr-