Ubuntu Server 12.04 + Wifi - WPA supplicant issues

Question

I've been trying (and failing) all weekend to get my homeserver connected via Wifi (I know it should be cabled, but a house move is imminent ;-). The setup is as follows:

• HP N40L Microserver
• Ubuntu Server 12.04 LTS 64bit
• Edimax EW-7612UAN V2 - USB Wifi adaptor
• Tenda N150 Wifi Router - run 1 SSID as b/g/n mixed mode, channel 6, WPA2 Personal, AES

On a fresh install of Ubuntu, my output is as follows:

ifconfig

ifconfig wlan0 up  

root@srv:/home/srvadmin# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:9c:02:a9:27:b9
          inet addr:192.168.0.106  Bcast:192.168.0.255  Mask:255.255.255.0
          inet6 addr: fe80::29c:2ff:fea9:27b9/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1226 errors:0 dropped:0 overruns:0 frame:0
          TX packets:534 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:124170 (124.1 KB)  TX bytes:78708 (78.7 KB)
          Interrupt:18

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:4 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:240 (240.0 B)  TX bytes:240 (240.0 B)

wlan0     Link encap:Ethernet  HWaddr 80:1f:02:4b:0e:9a
          UP BROADCAST 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)

lshw -C network

root@srv:/home/srvadmin# lshw -C network
  *-network
       description: Ethernet interface
       product: NetXtreme BCM5723 Gigabit Ethernet PCIe
       vendor: Broadcom Corporation
       physical id: 0
       bus info: pci@0000:02:00.0
       logical name: eth0
       version: 10
       serial: 00:9c:02:a9:27:b9
       size: 100Mbit/s
       capacity: 1Gbit/s
       width: 64 bits
       clock: 33MHz
       capabilities: pm vpd msi pciexpress bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=tg3 driverversion=3.121 duplex=full firmware=5723-v3.35 ip=192.168.0.106 latency=0 link=yes multicast=yes port=twisted pair speed=100Mbit/s
       resources: irq:42 memory:fe9f0000-fe9fffff
  *-network
       description: Wireless interface
       physical id: 1
       bus info: usb@1:5
       logical name: wlan0
       serial: 80:1f:02:4b:0e:9a
       capabilities: ethernet physical wireless
       configuration: broadcast=yes driver=rtl8192cu driverversion=3.2.0-29-generic firmware=N/A link=no multicast=yes wireless=IEEE 802.11bgn

iwconfig

root@srv:/home/srvadmin# iwconfig wlan0
wlan0     IEEE 802.11bgn  ESSID:off/any
          Mode:Managed  Access Point: Not-Associated   Tx-Power=20 dBm
          Retry  long limit:7   RTS thr=2347 B   Fragment thr:off
          Encryption key:off
          Power Management:off

Steps:
1. wpa_passphrase MySSID MyKey > /etc/wpa_supplicant.conf
2. wpa_supplicant -iwlan0 -Dwext -c/etc/wpa_supplicant.conf

The output is as follows:

root@srv:/home/srvadmin# wpa_supplicant -iwlan0 -Dwext -c/etc/wpa_supplicant.conf
ioctl[SIOCSIWENCODEEXT]: Invalid argument
ioctl[SIOCSIWENCODEEXT]: Invalid argument
Trying to associate with c8:3a:35:2c:63:28 (SSID='MySSID' freq=2437 MHz)
Associated with c8:3a:35:2c:63:28
Authentication with c8:3a:35:2c:63:28 timed out.
CTRL-EVENT-DISCONNECTED bssid=00:00:00:00:00:00 reason=0
ioctl[SIOCSIWENCODEEXT]: Invalid argument
ioctl[SIOCSIWENCODEEXT]: Invalid argument
Trying to associate with c8:3a:35:2c:63:28 (SSID='MySSID' freq=2437 MHz)
Authentication with c8:3a:35:2c:63:28 timed out.

If I try to force a DHCP request with wpa_supplicant -B -iwlan0 -c/etc/wpa_supplicant.conf -Dwext && dhclient wlan0, it just seems to hang and I can see DHCPDISCOVER requests in syslog.

I must be doing something silly to get stuck, when other posts make it look so simple (e.g. How do I connect to a WPA wifi network using the command line?).

Does anyone have any ideas on how to resolve this?

Solution

Is your wireless network broadcasting your SSID? If not, you'll need to add

scan_ssid=1 

within your network {...} definition within your wpa_supplicant.conf file