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I'm very excited to get into my Raspberry Pi, but I am pretty useless when it comes to most hardware and networking issues.

I purchased a Edimax Wi-Fi Adapter, but I am having trouble getting it to work. I using the latest version of Raspbian (“Wheezy”) and have done full updates of the firmware and software.

When I go into the Wi-Fi configuration in the GUI, I can scan for and connect to my Wi-Fi router. So far so good.

However when I go to a web page I get an error saying:

Cannot resolve hostname.

I have also noticed that in the Wi-Fi configuration no IP address has been assigned (or at least no IP address is being displayed).

When I run ifconfig -a, I get the following:

eth0      Link encap:Ethernet  HWaddr b8:27:eb:cc:0d:97  
          inet addr:192.168.1.88  Bcast:192.168.1.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:52 errors:0 dropped:1 overruns:0 frame:0
          TX packets:31 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:5875 (5.7 KiB)  TX bytes:5868 (5.7 KiB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  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:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

wlan0     Link encap:Ethernet  HWaddr 80:1f:02:82:c1:ce  
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:1 errors:0 dropped:34 overruns:0 frame:0
          TX packets:1 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:155 (155.0 B)  TX bytes:155 (155.0 B)

Running sudo cat /etc/wpa_supplicant/wpa_supplicant.conf also seems to show everything correctly:

network={
    ssid="correct_ssid"
    psk="correct_password"
    proto=RSN
    key_mgmt=WPA-PSK
    pairwise=TKIP
    auth_alg=OPEN
}

How do I fix this problem?

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2 Answers

up vote 1 down vote accepted

If you getting a 169.254 address there are 2 possible reasons...1) your wifi has not associated with your router, or 2) it has and dhcp isn't setup correctly.

Use "iwconfig" to verify your wifi adapter has associated with a router? You should see your ESSID, Mode should be Managed, and the Access Point should have a MAC address.

If not, try using wpa_passphrase. My wpa_supplicant does not work with an unencrypted password, and replacing just 1 line psk= worked.

If you are associated, and the dhcp client (which comes pre-installed) isn't working (shouldn't need to apt-get anything) then try setting a static address via "if config wlan0 192.168.1.X" where X is any unused number not in your routers dhcp range.

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Thanks for your help Martin. if config wlan0 192.168.1.X did work. Ultimately it was a power supply issue though. I tried a few different power sources and when I finally tried my iPod charge it worked a treat! – Goonanism Dec 5 '12 at 17:17
up vote 2 down vote

The article WPA supplicant suggests triggering DHCP to request an IP address for the WLAN. As root or with sudo, do:

 dhcpcd wlan0
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Amazing Dan - that worked! I had to install dhcpcd first (using apt-get). It's given the wifi a strange IP address though - 169.254.107.225. Any idea why it wouldn't be 192.168.1.xx like every other device on the router? – Goonanism Nov 26 '12 at 8:09
The 169.254.X.X probably means that DHCP did not work. It looks like a fallback address assigned by the RPI. Can you ping the address from another machine on your LAN? – Dan M Nov 27 '12 at 13:35
Hi Dan, yeah, something is wrong, I've been meaning to update this comment accordingly but, you know, life. I could ping it the first time but after restarting and running the command again I can't. It also isn't connected to the internet and I'm still getting the cannot resolve hostname error. Thanks again for your help. – Goonanism Nov 27 '12 at 18:32
Is it connected directly to a RPI or through a powered hub? The Wifi dongle probably only starts to draw significant current when it turns its transmitter on (i.e. when it trys to get an ip address). – Dan M Dec 1 '12 at 13:44
Probably authentication is what happens first. You could eliminate authentication issues by starting with an unprotected guest network. – Dan M Dec 1 '12 at 13:52
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