OIT Networking & Monitoring Services

Workaround for "iPhone OS 3.2 on iPad Stops Renewing DHCP Lease, Keeps Using IP Address" Issue (Version 1)

iPhone OS 3.2 on the Apple iPad® 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.)

OIT has reported that issue to Apple, and we are continuing to work with Apple to provide them with technical data to resolve the issue.

Until there is a fix, the following temporary workaround prevents the iPad from malfunctioning in this way.

This is version 1 of our workaround, which we published April 19 2010. Although effective, it has been supplanted by a more convenient workaround we published June 14 2010. We recommend using the newer workaround.


Procedure

The workaround is to prevent the iPad from going to sleep while the device's 802.11 wireless ("Wi-Fi") interface is on. Follow these steps:

  1. Reconfigure the iPad so it never auto-locks the device (Settings -> General -> Auto-Lock -> Never).

  2. Every time that you finish working with the iPad, do one of the following:

    You need not select the same choice every time you finish working with the iPad. For example, you might normally select choice A or choice B, only relying on choice C when you forget to take any action.

    Please note that you must not simply put the device to sleep (e.g., by pressing and releasing the Sleep/Wake button) without first turning off the Wi-Fi interface. Putting the device to sleep while allowing the iPad to use Wi-Fi can lead to the DHCP malfunction.

Why do I need to reconfigure the iPad to never auto-lock the screen?

You may wonder why the procedure above requires that you reconfigure the iPad so that it never auto-locks the screen. (That is, it never goes to sleep automatically.)

It might seem that as long as you always end your work session by performing the steps in choice A or choice B, you'd avoid the problem. That's true, but it's unlikely that you will always remember to end your iPad work session by carrying out choice A or choice B. Sometimes you may forget. Other times you might step away from the iPad long enough that, were the iPad configured to auto-lock the screen, the device would eventually auto-lock the screen (go to sleep) while the Wi-Fi interface was still on.

Reconfiguring the iPad so that it never auto-locks the screen guards against that situation.


Caveats

This workaround relies on the customer carrying this procedure assiduously; it will not prevent the bug if the customer puts the device to sleep without first turning off the Wi-Fi interface.

We recognize that this workaround represents some inconvenience to the iPad customer. We view this as a temporary workaround to allow these customers the opportunity to use their devices on the campus network until there is a fix from Apple.

If a customer's iPad malfunctions, regardless of whether s/he is trying to use this workaround, OIT will still need to block network service for the iPad, to stop it from continuing to disrupt service.


Why is this Workaround Effective?

The DHCP client software on iPhone OS 3.2 on iPad malfunctions when the following conditions are met simultaneously: the iPad is not attached to a power source, the iPad is attached to a Wi-Fi network, and the iPad is asleep.

This workaround is effective because it doesn't permit the iPad to remain attached to Wi-Fi when it is asleep.


A service of OIT Networking & Monitoring Services
The Office of Information Technology,
Princeton University
Last Updated: 7:00 pm March 15 2011