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Re: Can Anyone Explain the over-all view of Wireless Networking?

Kent West:
> Now I get no dhcp offers received. I don't understand how ifup/down and
> /etc/modules and udev and /etc/network/interfaces and "wpa-conf
> /etc/wpa_supplicant/wpa_supplicant.conf" and iwlist/spy/scan/whatever
> and eth0 vs wlan0 vs sit0 and auto eth1 vs allow-hotplug eth1 and wep vs
> wep-key vs open vs wpa, etc, all work together.

/etc/modules contains module names that should always be loaded. You
shouldn't need that for your wireless card, the kernel generally loads
kernel modules for hardware it can find automatically.

Udev is responsible for naming the device and, I think, calling
userspace programs like ifplugd when a new device is inserted. Unless
you don't like the device naming, you can probably ignore it.

/etc/network/interfaces contains the configuration of all your network
devices. You can manually specify IP addresses or use DHCP and there are
some special commands you can use to configure wireless settings, VPNs,
bridges and probably loads of other things as well. You can even declare
"virtual" devices which don't really exist that can be used by other
tools (like wpa-supplicant).

Wpa-supplicant is a special tool for configuring wireless encryption
settings. Additionally, it can use virtual device names from the
`interfaces` file so that a specific network card can use different
configurations depending on the available networks. As I understand it,
your computer is stationary and doesn't use wireless encryption, so you
can ignore wpa-supplicant as well.

In your case you just need to:

- Make sure the right module (and possibly a related firmware blob) gets
  loaded for your hardware. That already appears to work correctly.

- Determine the device name udev assigns. That appears to be wlan0 in
  your case.

- Find out the SSID you want to connect to. That's probably "ACUwireless".

- Find out whether this network uses encryption. ACUwireless doesn't.

- Find out whether you have to configure a static address, gateway and
  DNS server or whether you just need to enable DHCP.

For DHCP and no encryption put the following in the `interfaces` file:

auto wlan0
iface wlan0 inet dhcp
    wireless-essid ACUWireless

That should be it. Just run '/etc/init.d/networking restart' and
everything should be fine. You just might want to kill all dhclient
instances before doing that.

If it doesn't, first check whether your card is actually associated to
an AP. Just run 'iwconfig wlan0' and look for the second line:

wlan0     IEEE 802.11abgn  ESSID:"landfill"  
          Mode:Managed  Frequency:2.412 GHz  Access Point: 00:90:4C:5F:00:2A   

After "Access Point" there should be a hexa-decimal string just like in
my example. If this looks fine but DHCP still doesn't work, I am
temporarily out of ideas. :)

In public I try to remain calm and to appear perceptive.
[Agree]   [Disagree]

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