Q: Mountain Lion no Wifi after wake from sleep

They had me try that and it acted up again while I was still on the phone with them.

How early is to early? 

Some of the fixes I've tried last 4 days. 

I've noticed over time just like in Lion my drops have become farther and farther appart.  With that the drops I experience now lock the whole computer up unlike Lion.

I never had any WiFi problems with Leopard, Snow Leopard or Lion, so the fact that again the WiFi has failed on wake from sleep with 10.8.1 means the problem is still there, don't think it's too early to say that it doesn't fix it.

Based on your suggestion I looked a bit further into my router settings and this time you appear to have solved it for me!

I originally only noticed that you had been using WEP and I had always been using WPA, but I checked my settings and changed them from WPA (with TKIP encryption) to WPA2 (with AES encryption) and for the first time since the Mountain Lion upgrade my iMac now reconnects after wake from sleep, every time. Slower in connecting than it used to be, but every time it now reconnects. Thanks for the suggestion!

Hard reset of the router, changed the (dual) channels, and <Knock on wood> it worked - at least once. Here's hoping it will continue . . .

I posted something like that on another thread.  It was the biggest improvement I've tried.  I know some have tried it and it was working for them.  My post was for Actiontec Routers for Verizon Fios. 

The only thing that has sort of worked for me is 1. remove known networks, 2. turn off wifi, 3. restart computer with wifi off, 4. after restart turn wifi back on, 5. select network. It's a pain but more often than not it seems to work. This is a network with WPA2. When I was on a WEP network I had zero problems. This could mean the problem is with the network (it does have it's own unrelated issues) but I'm not 100% sure it's the only thing causing this.

yes, there are routers that support only WEP, but not WPA.  My supports only WEP, and if I change to WPA i have many disconnection and reconnections, so it doesnt work good.

I had this problem whith reconnecting after sleep, so i solved it with deleting all networks in system preferencs/networks and deleting all "Airport network password" fields in applications/utilities/keychain access, and after that restarting computer.

The point is to delete all "Airport network password" in   applications/utilities/keychain access whereever you can find it like login, system, system roots etc. and after restarting computer connect ot existing network.

I have only experienced this problem since upgrading to Mountain Lion.

I have a 13-inch Aluminum Late 2008 MacBook connected to an Apple Airport Extreme wireless router with WPA2 Personal set for the wireless security.  I also use a Magic Mouse connected through Bluetooth.  The set-up was the same for Lion and Snow Leopard having no issues.

Parallels is installed, but not Transmit.  Parallels has not been running when I have had the issue, and there are no Parallels related items in my Login Items.  I need to research more to understand if there are hidden processes that are being run automatically.

The problem is intermittent but frequent enough to be both noticeable and irritating.  To keep from using the power button, I am able to launch Terminal and do a ...

% sudo shutdown -r now

...which reboots the box, hopefully nicely.

I have attempted removing all known networks and readding just my wireless network after a fresh boot but still experienced the problem.

I am now trying to characterize whether the problem is coincident with the number of network connections (browser tabs, e-mail, etc.) open when the machine goes to sleep.

I do not have Transmit, and my issue is not connecting to wireless on waking from sleep.

Reading through more pages of this topic, I see several have also tried setting their drives not to sleep.

That reminded me of a similar issue I had on my iMac.  It would freeze and never wake from sleep until I set the SSD to not sleep.

I recently upgraded my MacBook with a SSD, and I am trying that setting to see if it provides relief.

Out of curiosity, many folks on this thread using traditional disks?

Howdy,

As some others have noted I'm seeing the same behavior with an Ethernet connection on my mid-2011 iMac and OS X 10.8.1. I have noticed that the problem of not re-connecting to my Time Capsule upon wake seems to occur when the system wakes from sleep shortly after the DHCP lease time has expired. I reset the lease time on my Time Capsule (a home network so I don't have lots of folks signing on and off) to 12hr from 4hr to reduce the probability of re-connect failure but that isn't really a solution. And I had it happen yesterday evening when I woke the system shortly after the lease had expired.

Good Luck,

Herb Schulz

I turned off sleep mode and have had no problems since.  Obviously, this is probably not the best thing for the computer long term.  I saw this morning that an update has been released.  I wondered if anyone has installed that and can share whether it fixes the problem?

The update didn't fix it for me, only the switch from using WPA to WPA2 that I posted earlier in this thread. Since switching to WPA2, it has connected after wake from sleep every time by itself without fail, just as it used to with Lion.

I just checked that setting, and mine was already set to WPA2....