用命令连接无线网的问题

[wingfy01]

用的是自带的驱动，然后我在/etc/network/interfaces里设置成非自动启动就是去掉auto；开机手动启动无线网卡，用ifup wlan0命令，当然在interfaces里设置成dhcp， mode是auto，但是每次用ifup wlan0 后总是显示：
Error for wireless request "Set Mode" (8B06) :
SET failed on device wlan0 ; Invalid argument.
Internet Systems Consortium DHCP Client V3.1.1
Copyright 2004-2008 Internet Systems Consortium.
All rights reserved.
For info, please visit http://www.isc.org/sw/dhcp/

wmaster0: unknown hardware address type 801
wmaster0: unknown hardware address type 801
Listening on LPF/wlan0/00:1f:3b:44:11:27
Sending on LPF/wlan0/00:1f:3b:44:11:27
Sending on Socket/fallback
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 5
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 6
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 9
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 13
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 17
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 7
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 4
No DHCPOFFERS received.
No working leases in persistent database - sleeping.

我之只能ifdown wlan0,然后再ifup wlan0；反复多次后才连上无线网!这是为什么？
弱弱的问问下，我用ifup wlan0，系统会用到interfaces文件吗 ？我的interfaces是：
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
iface wlan0 inet dhcp
# wireless-* options are implemented by the wireless-tools package
wireless-mode auto
wireless-essid NETCORE
wireless-key1 ABCDEF0987
# dns-* options are implemented by the resolvconf package, if installed
dns-nameservers 192.168.1.1
#The primary network intreface
#auto eth0
#iface eth0 inet static
#address 192.168.1.110
#netmask 255.255.255.0
#gateway 192.168.1.1
#network 192.168.1.0
#broadcast 192.168.1.255


还有wmaster是干什么用的：


wmaster0 Link encap:UNSPEC HWaddr 00-1F-3B-44-11-27-6C-6F-00-00-00-00-00-00-00-00
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)