mac os x

Symptoms

• AirPort wireless connection randomly stops working, even though signal strength to base station is good.
• Wireless connection strength drops, clicking on AirPort starts scanning, wireless strength returns to full, but Internet connection is lost.
• Can’t create wireless connection to DLink DIR-625 wireless router after upgrading to 10.5.2.

Possible Causes

• AirPort attempts to connect to stronger “Recent networks” listed in preferences file /Library/Preferences/SystemConfiguration/com.apple.airport.preferences.plist
• Apple has updated its AirPort wireless connectivity to a more recent draft of the “wireless n” proposed standard. This is a faster version of wifi than the previous 802.11 wireless g, b, and a standards. (References: Wikipedia 802.11, Discussions at Apple.com).
• [Added 080618]: AirPort is finding neighboring wireless router base stations on the current wifi channel and is attempting to connect to them. (References: Gedblog, TUAW.com)
• [Added 080824]: AirPort attempts to connect to based stations listed in “Preferred networks”, listed in System Preferences => Network => Advanced => AirPort => Preferred Networks. See the fix for AirPort Preferred Networks problem.
• [Added 090105]: Real Player Downloader.  Mechanics of problem unknown. See comment below by Jerry Zakariasen.

Diagnostics

• [Added 080618]: AP Grapher reports on nearby wireless internet base station signals. This is useful in determining if you’re having interference or competing wireless access point problems. If this is the case you can try changing wireless channels on your router.
• [Added 080618]: iStumbler is another wireless base station search tool similar to AP Grapher that you may find more to your liking.

Fixes/Solutions/Workarounds

Please, before implementing any of these fixes, try them one at a time and wait to see if there is any improvement in the situation before trying the next. Keep track of which fixes you have tried and report back when one of them (or none of them) in particular solved your problem so that we know which solutions are useful and which are less likely to help, thus moving forward in our knowledge of how to diagnose and fix wireless dropouts on Apple AirPort connections. Many thanks. ~ Ben.

• Backup /Library/Preferences/SystemConfiguration/com.apple.airport.preferences.plist file, then delete it. Reboot. Leopard will create a new AirPort preferences file with a single entry with your current wireless base station.
• For D-Link DIR-625 wireless router (from discussions.apple.com):
  1. Within Setup => Advanced => Advanced Wireless, change RTS Threshold to 2306
  2. Change Fragmentation Threshold to 2306
  3. Use “Mixed 802.11n, 802.11g, and 802.11b” within Setup => Wireless Settings
• [Added 080618]: Change wireless channel on your wifi router (e.g. AirPort Extreme base station, NetGear, Linksys) from 6 (the default) to anything from 1-4 or 8 to 11. Please refer to your router’s instruction manual on how to do this. The reason for avoiding channels 5 and 7 is that wifi routers by design will automatically switch to one channel above or below their current channel when wifi signal noise passes a certain value. Thus, if you were having problems on channel 6, your router and AirPort have already tried channels 5 and 7 and you’re still experiencing problems.
• [Added 080618]: If possible, use the 5Ghz transmission frequency/band for your wireless router. Most wireless devices (nearly all wireless routers and cordless telephones) in homes use the 2.4Ghz transmission band. Avoiding this band will result in much less radio noise. Again, this is a setting on your wireless access point rather than on your Mac. Please refer to your wireless base station’s instructions on how to change radio frequency (if possible).
• [Added 080618]: Keychain Access is an Apple program that saves passwords to websites, to your Mac itself, to wireless base stations, etc. The keychain entries related to wireless base stations is a potential cause of wireless drops in Leopard 10.5.2 with the theory being that Keychain Access was modified in this release, breaking (somewhat) keychain items created in older versions (10.5.1 and prior). Deleting and recreating the keys in 10.5.2 and beyond may resolve this issue if you are affected.Launch Keychain Access within Finder: Applications => Utilities => Keychain Access. On the top left, select System, underneath login. Find the name of your wireless base station or router, often called an SSID in networking terms. For me it’s WANADOO-D310. Under the Kind column it should read AirPort network password. You may find multiple keychain entries for wireless base stations you’ve used in the past. We want to delete them all, but before doing that, save their passwords. You do this by right clicking on the item, for me WANADOO-D310, and choosing Copy Password to Clipboard. If you are asked to allow access to this item by kcproxy, click Allow.
  Then create a new text file somewhere on your mac and paste the password that’s been copied to your clipboard. This will make it easier when you have to reconnect to this base station. You might want to note which base station/wireless router this password is related to while doing this. I did this by simply writing the name of the wireless router beside the password. After backing up the passwords, delete all the keychain items of kind AirPort network password. Now turn off the AirPort connection by clicking on the AirPort menu bar icon (looks like the image at the top of this post) and selecting Turn AirPort Off. Open System Preferences => Network. You’ll notice that Network Name select list will no longer have your base station listed. Click Turn AirPort On. AirPort will search for wireless networks (takes about 30 seconds) and will eventually pop up with a window saying None of your preferred networks are available, but you should see your wireless base station listed as one of the networks.
  Select your network and click Join. You’ll be asked for your password. Hopefully you remembered to save that password somewhere and can simply copy and paste it back in. (Use right click => Paste rather than Apple Key + V, which won’t work for this password field). After this you should be reconnected to your wifi base station. If you return to your Keychain Access window, you should once again see your base station listed with the System Keychains. You can close the Keychain Access and Network preferences pane windows. If you have multiple wireless networks that you use often, you’ll have to search and reconnect to them with the passwords you’ve saved. Hopefully the recreated keychain items will keep you connected.
• [Added 080624]: Remove Preferred Networks. From within System Preferences => Network => Advanced => AirPort, using the minus button, remove all preferred networks except for the current wireless access point you’re connected to.
  
• [Added 090105]: Remove Real Player Downloader. Jerry Zakariasen mentions in the comments below that uninstalling Real Player Downloader for Mac has fixed wireless network drops on his mac.  See his comment below for more details. Thanks Jerry.

Background

Just after upgrading to 10.5.2 I noticed that once in a while my AirPort wireless connection would drop to 2 or 3 bars, then return to full signal strength, but I couldn’t access the Internet after that. There didn’t seem to be any pattern to these dropouts of wireless connection. No interference from neighboring base stations either. Yet everything was ultra stable with 10.5 and the only change I made was upgrading (finally) to 10.5.2.

After doing some research, I had a theory that AirPort was searching through old wireless connections within /Library/Preferences/SystemConfiguration/com.apple.airport.preferences.plist constantly looking for a better signal. And whenever the current wireless connection suffered from minor transient interference (say cordless telephones), it would immediately try to connect to another base station or try to switch to a different channel. Have a look at your version of the airport preferences file by navigating to it in Finder, starting with Macintosh HD, then Library, Preferences, and finally within the SystemConfiguration folder. You can simply hit enter with the file highlighted to use Quick Look. You can also use Terminal to quickly print the file to the screen with the following command: cat /Library/Preferences/SystemConfiguration/com.apple.airport.preferences.plist

Once the AirPort control software in 10.5.2 set about trying to find a better wireless connection, it would never successfully get back your original wireless connection which was really fine. Hence, from time to time, you would see a slight drop in wireless signal strength, then after clicking on the AirPort wireless icon, it would scan for networks for a few seconds, then return to full strength, yet you would have already lost Internet access.

The fix is simple:

1. Drag the /Library/Preferences/SystemConfiguration/com.apple.airport.preferences.plist file to your desktop (as a backup),
2. Delete the file within SystemConfiguration,
3. Reboot and let Leopard create a new airport preferences file with only your current wireless connection listed within it.

With only one base station listed in “Recent Networks” within the file, AirPort won’t try scanning for other stronger networks and you’ll stay connected.

That’s the theory anyways. It’s worked for me so far. Hope it helps you too.

Leave a comment if you have questions or have tried the fix with success/failure.

Apple has just released Mac OS X 10.5.3 update and the changes are not earth shattering.

Here is a list of changes in Leopard OS X 10.5.3 posted at Apple Support.

Most important to me would be this one:

“Addresses reliability issues when performing a full restore from a Time Machine backup.”

[Hint: don't install the Leopard 10.5.3 update for a week or two if you aren't suffering from any of the problems fixed in the list of changes. Why? Remember 10.5.1? That was a fiasco that led to so many problems that 10.5.2 was quickly released to "fix the fixes". Basically, let others find the bugs within 10.5.3 and have Apple fix those before you install the update. If there are any major issues with this latest release, you'll avoid the worst of them by waiting a couple of weeks. I'm actually still using 10.5.0 since it's rock solid and the updates released since don't affect my day-to-day usage. I'd rather have reliability than having all the software that I don't use up-to-date.]

That’d be pretty annoying to use Time Machine religiously and when finally disaster strikes and your backups aren’t fully useable? Ouch.

Regardless, I’d still recommend SuperDuper! for bootable Leopard backups in concert to Time Machine file backups, since Time Machine’s backups do not give you a bootable backup disk to restore from. If Time Machine backups are all you have, you’d have to reload Leopard from DVD, then restore your settings and documents from Time Machine.

With SuperDuper! you could simply connect the drive you used via FireWire/USB, reboot your Mac, hold down the alt key, select your SuperDuper backup and be working from that drive like nothing has changed.

Even more hard-core, you could simply remove the failed drive within your Mac, install the SuperDuper disk in its place, boot, and theoretically you should be operating normally as if nothing had happened.

Open Finder

Go to Applications => Utilities

Double click on Terminal or highlight Terminal and Apple/Command Key + Arrow Down.

The following is a summary of how I created a dual boot setup of OS X Leopard (10.5) and Tiger (10.4) on a MacBook Pro, keeping the original Tiger installation intact and available through alt/option booting during system startup. Always Always Always make a backup before you try any shenanigans like I do below. The best way to do this is with an external drive connected to your machine via FireWire or USB 2.0 and using cloning software such as SuperDuper!

Step One: Boot from Leopard

Boot from the Leopard install dvd to allow repartitioning your Tiger-installed hard disk without erasing the disk first. Insert the Leopard install DVD into the dvd drive. Ignore the pop-up Finder window. Shut down your Apple computer (don’t use restart). After your Apple has shut down fully, press the power button to start it.

When you hear the power-on “chime”, press and HOLD the Option button (just left of the Apple/Command key, also known as Alt or two horizontal lines, one diverging before connecting with the other). If for some reason your Mac doesn’t make a noise when you boot up, just press and hold the Option button when the screen lights up. Hold the Option button down until you see a grey screen with two (or more) options displayed. One of which will be a picture of a hard disk and another of the Leopard OS X Install DVD. You may have more bootable disks to choose from if you have more than one partition on your hard disk.Using the arrow keys, move to the Leopard Install DVD and hit Enter. This will boot into the Leopard install program.

DO NOT hit continue when the Leopard install window has loaded.Using the mouse, navigate up to the top menu bar and choose Utilities, then Disk Utility. Once Disk Utility has loaded you should see your Apple computer hard disk, the Leopard install dvd, and possibly other disks if you have them attached to your computer.

Choose the hard disk that you want to install Leopard on. By default this should already be selected. For me the Disk is a 111.8 GB Fujitsu MHW2… drive with Macintosh HD underneath it (that’s the volume, within the Macintosh hard disk, you can have multiple volumes inside one hard disk). From here you should see the partition map of your Macintosh HD hard disk, a rectangle standing tall, outlined in blue.

Above the right hand side window will be five choice buttons: First Aid, Erase, Partition, RAID, Restore.

First Aid:You will want to Repair your Macintosh HD before doing any partition changes, regardless of whether you know it is verified or not already. Paritioning will fail if the disk is not error free and verified within this install session. Verifying the disk within Tiger does not mean that Leopard Disk Utility will consider the drive error free as was the case with my install. Thus, repair the disk once you get to this step, even if you had previously verified the disk in Tiger.

Step 2: Resizing + Creating Partitions

After Verify Disk step is completed, we’ll resize the current Macintosh HD Tiger partition and create a second Leopard partition with the free space. NOTE: The resize and creation of a secondary partition will LIKELY FAIL if you have Parallels installed in your Tiger system disk/volume. For the repartitioning to complete without “no space left on device” error, I was forced to delete my Parallels Windows XP SP2 virtual disk, which was roughly 10GB in size.

There are some files that Disk Utility Partition program cannot move when performing its resize and repartiton operation. The Parallels virtual disk file is one of these immovable files. When Disk Utility comes across this file, repartitioning failed with the error: “no space left on device”. The solution in my case was to reboot back into Tiger, load up Parallels, and simply delete the virtual Windows XP installation (I skipped deleting the floppy drive) which deletes the virtual disks as well. I chose this because my Windows XP install is already backed up onto an external USB 2 drive clone of my Tiger system created through SuperDuper!. I’m guessing that you can simply move this file off to some secondary external drive, replace it after, and everything will be handy dandy, although I have not tested this.

EDIT: Yozlet mentions in the comments below that removing large files (1GB+) can also help avoid the dreaded “no space left on device” error while repartitioning the drive. Here are some tips on finding and removing old files on your Mac to avoid the “no space left on device” error.

Click and drag the bottom right hand corner of the Volume Scheme (the blue outlined rectangle which represents your disk, Macintosh HD) and drag it upwards, making the volume smaller. I chose around 30GB for the Macintosh volume, out of the entire 110GB disk. This leaves a healthy chunk (80GB) of unused disk space on the drive. Beneath the blue rectangle Volume Scheme there are plus and minus buttons. The plus button when clicked will add a partition to your disk. Click this to add a generic volume onto which we will install Leopard. After clicking the plus button for adding a partition, I again had to adjust the size of the Macintosh HD volume where Tiger resides, back down to about 30GB. After this, click Apply, then Partition on the pop-up window. Go make some coffee while it does the partitioning.

After you’re well caffinated partitioning should be finished and you’ve got a pristine empty partition on which to install Leopard.Exit out of Disk Utility and you’ll see the Leopard install screen again. Click Continue from here and you’ll be asked where to install Leopard. Here we choose Leopard on our hard disk. After that, continue with the install as per normal.

Step 3: Transfer

Near the end of the Leopard install the setup program will ask if you already own a Mac and want to transfer previous settings and applications. For this step choose from another volume on this Mac. Obviously the volume we’ll use is the Tiger volume that we’ve preserved on this computer. After that, I choose User files and settings, Applications and network settings. You can choose what you desire here, but I left it at that. Any programs or settings that didn’t make it over should be easy enough to replace, reinstall after. This step can take the better part of an hour depending on how much data you’re transferring.

Best of luck. Keep that backup handy.

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