Getting a new wireless IP link without rebooting.

[Tod Merley]

>
>
> Date: Wed, 8 Feb 2006 16:31:04 -0500
> From: Robert Cahn <robertscahn at gmail.com>
> Subject: Getting a new wireless IP link without rebooting.
> To: fedora-list at redhat.com
> Message-ID:
>         <5f7024460602081331u6f85b6a6me2334ff203093432 at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> I have a FC4 desktop.  Every once and a while the 802.11 link fails in the
> sense that DNS stops working.  I have tried to inactivate the link and
> bring
> it up again but when I do so I get "Determining IP information for eth0...
> failed; no link present.  Check cable?"  Eventually I give up and reboot.
> Is there anything else I do that is less disruptive and will restore
> communication?
>
> Bob Cahn
> Gipsy Trail Club
> Carmel, NY
> RobertSCahn at gmail.com
>
Hi Bob!

If "Determining IP information for eth0" failed (assuming that eth0 is your
wireless 802.11x link) then perhaps the link has gone down, or perhaps it is
trying to attach to another AP.

Probably a good time to open a terminal (Applications > System Tools >
Terminal) and then type:

su

Which will (after you apply the root password) make you the root user - then
type:

/sbin/ifconfig

Which will show a lot of information about your networking.  You should look
to see that your wireless device is attached to an IP (like 192.168.0.3 for
example).  Also type:

/sbin/iwconfig

Which will show much information about your wireless link.  Look for proper
ESSID (name of your Access Point - the name assigned to your wireless modem
probably) and take a good look at signal levels and any errors that are
counted.  If there is a problem where interference or faulty hardware is
causing the link to become unstable it may show here.

If you find a good IP for your wireless device, and if the wireless info and
ESSID also look good then try:

ping 192.168.0.1

Assuming that your modem's IP address is indeed 192.168.0.1.  It's replys
every second (you stop this with a ctl-c (hold down the Ctrl key and tap c))
tell you soon if you have a connection with your modem.  If you do, then
look at /etc/resolv.conf by:

cat /etc/resolv.conf

Those designated as dns servers will probably include your modem.  This is a
long shot but if all has been good to this point and if there are at least
two dns servers in reslov.conf comment out the one with your modem's IP -
close your browser and re-open and see if you have good browsing.  I
actually had a problem with a modem which would not reslove IPv6-dns.  Best
solution (easiest anyway) was to eliminate the DNS calls to it by taking it
out of /etc/reslov.conf.

If you find that the wireless link is showing errors, try changing the
wireless channel used or moving the access point (probably your modem)
closer to your computer.  Someone may have lit up wireless near you on the
same channel perhaps.

All of the above commands can be used at any time and would be good to run
to establish your working baseline.

Good Hunting!

Tod
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