OIT Network Systems

Workaround for "iPhone OS 3.2 on iPad Stops Renewing DHCP Lease, Keeps Using IP Address" Issue (Version 2)

iPhone OS 3.2 on the Apple iPad® (first generation) malfunctions in a way that interferes with network service to others. (A detailed description of the issue is at iPhone OS 3.2 on iPad Stops Renewing DHCP Lease, Keeps Using IP Address.)

The following workaround prevents the device from malfunctioning in this way.

This is the second version of our workaround. It replaces an older version. Although both versions are effective, this newer version is more convenient. We recommend using this newer version over the older version.

OIT reported this issue to Apple. Apple fixed the bug as of iOS 3.2.1.


Procedure

  1. Turn off "Push" (i.e. Microsoft Exchange ActiveSync) support for all mail, contacts, and calendar accounts. Do so using: Settings -> Mail, Contacts, Calendar -> Fetch New Data -> Push -> Off.

    Using this setting to turn off "Push" support for mail, contacts, and calendar accounts will override any per-account settings at: Settings -> Mail, Contacts, Calendar -> Fetch New Data ->Advanced.

    You may still choose to set a schedule for periodically fetching such data, using the lower portion of the Settings -> Mail, Contacts, Calendar -> Fetch New Data screen.

  2. Turn off "Notifications" (Apple Push Notification Service). Doing so can be a little tricky, because the setting appears and disappears depending on the applications installed. Begin by checking the Settings application for a Notifications category.

    The Settings -> Notifications category appears if your iPad presently has any applications installed which support Apple Push Notification Service. None of the applications pre-installed in iPhone OS 3.2 support Apple Push Notification, but many such applications are available in the App Store.

  3. If the "Settings" application is still running, quit the "Settings" application by single-tapping the "Home" button.

  4. Reboot the iPad. This is to workaround a problem we have sometimes seen, in which the configuration changes made above sometimes don't take full effect until the iPad is rebooted. Reboot the iPad as follows:

    1. Turn off the iPad by pressing and holding the Sleep/Wake button for a few seconds until the red "slide to power off" slider appears on the screen. Release the Sleep/Wake button. Drag the slider to power off the iPad.

    2. Turn on the iPad by pressing and holding the Sleep/Wake button until the Apple logo appears on the screen. Release the Sleep/Wake button.

  5. Be aware that when you launch any application that support "Notifications", your device may sometimes display an alert suggesting that you turn on Notifications.

    For example, it may display an alert that says: Turn on Push Notifications to Allow "ApplicationName" to Receive Sounds, Alerts and Badges along with a button to Cancel and a Settings button that launches the Settings application and enters the Settings -> Notifications screen.

    Despite frequent alerts of this nature, you will need to remember to not turn on Notifications.

  6. Be aware that if you were to delete all installed applications which support Apple Push Notication Service, the Settings -> Notifications category will disappear, and the iPad will forget that you turned off Apple Push Notifications. If later you were to install any application which supports Apple Push Notification Service, the Notifications category would re-appear in Settings, but would be reset to On. At that time you would need to change this setting to Off.

    To avoid encountering that issue, ensure you always keep installed at least one application that supports Apple Push Notification Service.


Caveats

We recognize that this workaround represented some inconvenience to the iPad customer. We viewed this as a temporary workaround to allow these customers the opportunity to use their devices on the campus network until there was a fix from Apple. Apple fixed the bug as of iOS 3.2.1.

This workaround involves disabling "notifications" (Apple Push Notification Service), and involves disabling "push" support for mail, contacts, and calendar account. Naturally, any services or applications which rely on either of those features will be affected. For example, Apple's "Find My iPad" service (available to Apple MobileMe® subscribers) is not available.


Why is this Workaround Effective?

The DHCP client software on iPhone OS 3.2 on iPad (first generation) malfunctions when the following conditions are met simultaneously: the device is not attached to a power source, it is asleep, and the device chooses to remain attached to a Wi-Fi network while in that state.

This workaround is effective because it appears to result in the device choosing to disconnect from the Wi-Fi network when it is simultaneously not attached to a power source and it is asleep.


If You Were Using our Previous (Version 1) Workaround

Previously we published a different workaround: to use the iPad in such a way that the device would never be put to sleep with the Wi-Fi interface enabled. Typically this involved the customer manually disabling the Wi-Fi interface prior to putting the device to sleep. It also involved reconfiguring the iPad to never auto-lock.

That workaround was effective, but we believe this new workaround is better because it is more convenient for nearly all customers.

If you were previously using the old workaround, you can stop using it when you switch to using this new workaround.

One part of the old workaround was to reconfigure the iPad so it would never auto-lock. Once you switch to the new workaround, you may reconfigure the iPad to auto-lock if you wish; do so at Settings -> General -> Auto-Lock.


A service of OIT Network Systems
The Office of Information Technology,
Princeton University
Last Updated: 7:00 pm March 15 2011