A few weeks ago, I brought home my work laptop so that I could take care of some tasks over the weekend.  I have done this before, so it already knew my wireless network and connected just fine.  However, even though it as connected, it stated that “No Internet Access”.

This was puzzling…  The wireless was definitely working, and my other computers and devices were connected just fine, so clearly the problem wasn’t the network.  I tried disable and re-enabling the wireless adapter, but no luck.  I was in a rush, so I ended up plugging in an old fashioned ethernet cable from my router, and my laptop was able to access the internet just fine.  It solved my problem and I didn’t troubleshoot further.

This weekend, I needed to bring my laptop home again, and I ran into the same issue – it would connect to the wireless but was unable to access the internet unless it had a physical cable.  I decided to spend some more time troubleshooting this time and figured it out.

I opened a command shell (Start > Run > cmd.exe) and ran “ipconfig”, which displayed all of my wireless adapter information.  The default gateway showed my router’s address (169.198.0.1), but the IP address for the computer was not a 169.198.0.x address.  Instead, it was an address that I recognized as belonging to my corporate network at work.  For some reason, even though the laptop had connected to the wireless, it hadn’t given up its old wireless IP address and obtained a new one for this network.  As a result, it wasn’t able to route traffic properly, causing it to think that internet access was unavailable.

I spent a while looking at my network settings to see if my IP address was somehow manually set, but it wasn’t.  I have no idea why it wasn’t getting a new address.

I decided to force my laptop to obtain a new address.  I opened the command shell again and ran “ipconfig /release”, which forced it to let go of any ip addresses it was holding on to.  At this point, my wireless network icon changed from a “connect but no internet access” image to a “searching” image.

I then ran a second command, “ipconfig /renew”, which would tell it to try to re-establish connections for its IP addresses.  My wireless network icon promptly changed back to a connected image, and this time, it claimed to have internet access!

I ran “ipconfig” again, and I saw that my ip address was indeed a 192.168.0.x address, which would mean that it could route traffic properly.

I still have no idea why it was holding onto the old address.  Getting a new IP address when switching between wireless networks seems like a pretty obvious step, but at least I now know how to quickly fix the problem if I ever run into it again.

A moment later