i try to connect to a wep protected wireless access point.

with the folowing configuration :
auto wlan0
iface wlan0 inet dhcp
 wireless-essid Intrawep
 wireless-key 9638520741
 wireless-mode managed
 wireless-enc on
 wireless-ap 00:0B:3B:3F:26:00

$ifup wlan0
Internet Systems Consortium DHCP Client 4.1.1-P1
Copyright 2004-2010 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/

Listening on LPF/wlan0/00:24:8c:42:86:db
Sending on   LPF/wlan0/00:24:8c:42:86:db
Sending on   Socket/fallback
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 3
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 3
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 3
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 3
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 3
NO DHCPOFFERS recieved
No working leases in persistant databases - sleepeng

$iwconfig wlan0
wlan0     IEEE 802.11bg  ESSID:"Intrawep"
          Mode:Managed  Access Point: Not-Associated   Tx-Power=27 dBm
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Encryption key:9638-5207-41
          Power Management:off


but if I configure this way :
auto wlan0
iface wlan0 inet manual

$iwconfig wlan0 key '9638520741' mode managed essid 'Intrawep'  enc on ap 00:0B:3B:3F:26:00
$dhclient -v wlan0
Internet Systems Consortium DHCP Client 4.1.1-P1
Copyright 2004-2010 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/

Listening on LPF/wlan0/00:24:8c:42:86:db
Sending on   LPF/wlan0/00:24:8c:42:86:db
Sending on   Socket/fallback
DHCPREQUEST on wlan0 to 255.255.255.255 port 67
DHCPACK from 192.168.1.1
bound to 192.168.1.19 -- renewal in 34338 seconds.

$iwconfig wlan0
wlan0     IEEE 802.11bg  ESSID:"Intrawep"
          Mode:Managed  Frequency:2.452 GHz  Access Point: 00:0B:3B:3F:26:00
          Bit Rate=36 Mb/s   Tx-Power=27 dBm
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Encryption key:9638-5207-41
          Power Management:off
          Link Quality=52/70  Signal level=-58 dBm
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0



I see two differences here :
ifup begin by a DHCPDISCOVER
dhclient use DHCPDISCOVER only if DHCPREQUEST didn't succeed
but DHCPDISCOVER should work too

The second difference is the configuration of wlan0 wich seems to be incomplete,
mainly ap not configured
and other option wich i do not know if they are important or not.

i guess the problem must come from the pre-up script wireless-tools, i have still not investigated further.

please tell me if you experience the same problem, if so it is a serious problem in this package.

It work with the following configuration :

auto wlan0
iface wlan0 inet dhcp
pre-up ! ifconfig eth0 | grep 'inet addr'
pre-up ifconfig wlan0 up;iwlist wlan0 scanning;sleep 2;
pre-down ifconfig -v wlan0 down
  wireless-essid Intrawep
  wireless-key 9638520741


somehow it appears that to be associated with any access points i need to :
1. Know the access point mac adress trough a call to iwlist scanning,
this call need the interface to be up first.
2. I need to wait two seconds to allow...ifup? to "receive" this
information so it can be used.


I guess it is not a bug in wireless tools so , but it make
wireless-tools pretty unusable in /etc/network/interfaces.

I add an hint for anybody with the same problem, if you seem to need
multiple call (twice in my case) to ifup to be able to associate with
any access points, it only meant that you need to WAIT, nothing else,
before calling ifup.