We mentioned this a couple weeks ago: iPads at Princeton don’t seem to want to help students, work, study, or stream Netflix. Thanks to MacRumors, we now have more information bout the issue. It appears that a workaround has been published by Princeton. We wanted to share this with our readers from that school. (Workaround is at the bottom of this page.) Princeton reports that they have seen a number of iPads with errors in their Dynamic Host Configuration Protocol (DHCP) protocol.
The malfunction we see is that the iPad uses DHCP to obtain a lease, renews the lease zero or more times (as expected), but then continues using the IP address without renewing the lease further. The iPad allows the DHCP lease to expire, but it continues using the IP address after allowing the lease to expire. The incident continues for some time (typically hours); usually it ends when the iPad asks for a new DHCP lease, or the iPad disconnects from the network.
Huh? What does that mean?
What this means is that iPads are slowly trying to use IP addresses already taken back and given to a different device. In other words, iPads are seen by the network as trying to hack into someone else’s computer. This apparently has nothing to do with the wi-fi issues some people have been claiming to have with their iPads. It’s a safety issue that has caused 9 of 41 iPads to be blocked from the network. According to Macrumors, Princeton’s current policy with respect to iPads is to allow them onto their network, and in the case of DHCP lease issues, notify the user and point them to the workaround. Only if problems continue after that point would a specific device be blocked.
-Sources include MacRumors and Princeton University
How do i fix it so my iPad works again?
Princeton has kindly distributed a workaround:
The workaround is to prevent the iPad’s screen from being locked while the device’s 802.11 wireless (“WiFi”) interface is on. Follow these steps:
- Reconfigure the iPad so it never auto-locks the screen (Settings -> General -> Auto-Lock -> Never).
- Every time that you finish working with the iPad, do one of the following:
- Choice A:Turn off the WiFi interface (Settings -> Wifi -> On/Off).After you have turned off the WiFi interface, you may choose to lock the screen (press and release the Sleep/Wake button). The screen will turn off.When you next wake the iPad and unlock the screen, you will need to turn on the WiFi interface (Settings -> Wifi -> On/Off) before you may resume using WiFi.
- Choice B:Turn off the iPad (press and hold the Sleep/Wake button for a few seconds until the red slider appears, then drag the slider).We really do mean “turn off the iPad”, not “lock the screen.” (Just pressing then releasing the Sleep/Wake button locks the screen; it does not turn off the iPad.)When you next wish to use the iPad, you will need to turn the iPad on (press and hold the Sleep/Wake button until the Apple logo appears).
- Choice C:Take no action; don’t even press the Sleep/Wake button to lock the screen.This will result in the iPad’s screen remaining unlocked. The screen will not turn off.You may find choice this inconvenient because the unlocked screen will continue to accept input, perhaps resulting in unintended operation of the iPad while the device is being transported or held.
The unlocked screen will draw more power than it would had the screen been locked; the battery will need to be recharged sooner.
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 lock the screen (e.g., by pressing and releasing the Sleep/Wake button) without first turning off the WiFi interface. Locking the screen while allowing the iPad to use WiFi 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.
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 while the WiFi interface was still on.
Reconfiguring the iPad so that it never auto-locks the screen guards against that situation.