OS X Mountain Lion: iMac may not automatically reconnect to Wi-Fi network after waking from sleep

Hi, this has worked for a few...

Make a New Location, Using network locations in Mac OS X ...

http://support.apple.com/kb/HT2712

10.7…

System Preferences>Network, top of window>Locations>Edit Locations, little plus icon, give it a name.

10.5.x/10.6.x/10.7.x instructions...

System Preferences>Network, click on the little gear at the bottom next to the + & - icons, (unlock lock first if locked), choose Set Service Order.

The interface that connects to the Internet should be dragged to the top of the list.

Instead of joining your Network from the list, click the WiFi icon at the top, and click join other network. Fill in everything as needed.

For 10.5/10.6, System Preferences>Network, unlock the lock if need be, highlight the Interface you use to connect to Internet, click on the advanced button, click on the DNS tab, click on the little plus icon, then add these numbers...

208.67.222.222

208.67.220.220

Click OK.

Also, turn off IPv6:

System Preferences » Network » AirPort » TCP/IP tab » Configure IPv6

Or whatever Interface you use.

Good news, thanks for the report! 🙂

I have a similar problem as henrry. I upgraded my MBP from SL to Mountain Lion, and each time after the display goes to sleep and I wake it, the internet connection has been terminated and what ever I was downloading at the time was cancelled. I have found it happens with Wi-Fi and Ethernet connections. I had no problems at all with Snow Leopard, regretting the upgrade to ML. I thought it was just my mac, but so many other people are having trouble too.

experiencing the same trouble with my iMac after installing the MountainLion

band new mac pro, if I set the tower to go to sleep, netwrk doesn't reconnect after waking. I fixed by turning off the setting for my computer to go to sleep. I actually have to restart my modem to get internet connection after waking from sleep. It is a annoying problem. I have found the energy saving setting and sleep functions of this system to be marginal at best. They don't work as advertied, and the problems that crop up when computer wakes are a nightmare. Every time I wake my computer I wonder what I am going to have to fix next.

Worked! Thanks!

Well here is a new fix that worked for me, Credits go to Topher Kessler, the original author. I provided witha link to the whole article at the end. Anyways I hope it helps! This is much easier than the prior fix.

Remove AirPort configuration property list
Many times problems with system services can happen after an upgrade if some corruption has occurred in the configuration files associated with those connections. In the case of Wi-Fi network connections, the options for auto log-in and other details about a specific network are saved in a configuration property list at the following location:

/Macintosh HD/Library/Preferences/SystemConfiguration/com.apple.airport.preferences.plist

Try disabling AirPort in the menu bar, go to that folder and remove the "com.apple.airport.preferences.plist" file, and then re-enable AirPort. Doing this will create a new configuration file that will not have any residual settings or options in it from you Snow Leopard installation, and therefore may prevent the autoconnect problem from occurring.

http://reviews.cnet.com/8301-13727_7-20095988-263/fix-wi-fi-autoconnect-problems -in-lion/

This worked for me. I'm finding that a lot of preferences need to be rebuilt in moving from 10.6.8 to 10.8.

Had the same issue and finally solved it. After the upgrade to Mavericks our 2 new Macbook Airs stopped connecting automatically to Wifi while the older machines the kids had still worked fine.

Bought a new airport extreme and problem solved. Our Airport Extreme was about 5 years old and was probably not compatible with the new OSX.

BTW this was after trying everything people suggested on this forum and a 4 hour marathon tech support call with Apple where we reinstalled the OSX.

***** to need to spend $200 but glad the problem got solved.

New extreme is also mega fast so its all good.