I use Ubuntu Dapper Drake as my main operating system. Sometimes I have difficulty connecting to wireless connections. I am writing this post to share what I have learned about using wireless Internet on Ubuntu.
My computer is an Lenovo (IBM) ThinkPad T43 with Centrino. I can usually just turn on the computer and be connected to a wireless signal. At other times, it requires some tinkering, and in the worst (rare) cases, it does not connect at all. But by following these steps, you should be able to troubleshoot most wireless connection problems in Ubuntu.
I am writing this post from the Fort Lauderdale International Airport in Florida, where there is an obvious wireless Internet signal. My laptop is connected to the signal, but cannot connect to the Internet.
Below is a screenshot of my current Connection Properties. You can find this tool in the upper right corner of your Ubuntu GNOME desktop.
It shows that the signal strength is 96%. I clicked on the Configure button to get to the next screen shown below:
I double-clicked on the eth1 interface (my wireless card), and got to the next screen. I changed the Network Name (ESSID) by clicking next to the input box.
After clicking the "OK" buttons, I still couldn't connect. I typed iwlist eth1 scanning in the terminal to see a list of all wireless signals in the area as shown below:
That didn't provide any additional information. I also tried the command iwconfig, which shows more information about a wireless connection.
Finally, I went back into the Network Connection Properties tool and clicked on the DNS tab. I saw that my previous t-mobile connection from earlier in the day was listed in my Search Domains box, as shown by the red arrow below. As soon as I deleted that, I was able to connect to the wireless Internet signal.
Sometimes I find that I have to deactivate the wireless interface, click all of the "OK" buttons, and then re-enable it before it will work. I'm not sure why.
If you have installed a firewall, it may be interfering with your wireless connection. If you can't seem to connect no matter what you do, try disabling the software firewall.
If all else fails, set up the connection settings the way that you think they are supposed to be. Then reboot the computer. Sometimes that works.
There are several other command line tools that relate to wireless networking, but they don't really apply here. More information about them can be found in the man pages for iwconfig.
If you have any information to add to what I've written here, please leave a comment.