iPad not properly renewing DHCP lease, causing problems for Princeton IT


Princeton University IT, which keeps a close eye on their infrastructure, claims the iPad is not being a good network citizen:

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.

Princeton says they're communicating with Apple to resolve the issue, but in the meantime they -- and other large institutions -- are keeping the misbehaving iPads off their network.

This won't be an issue for a home user or anyone on a small network where IP conflicts are unlikely, but it's something Apple will need to fix in the near future, especially for the education market for which the iPad is so well suited.

Have you noticed any iPad problems on your network? Let us know in the comments!

Have something to say about this story? Leave a comment! Need help with something else? Ask in our forums!

Rene Ritchie

EiC of iMore, EP of Mobile Nations, Apple analyst, co-host of Debug, Iterate, Vector, Review, and MacBreak Weekly podcasts. Cook, grappler, photon wrangler. Follow him on Twitter and Google+.

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Reader comments

iPad not properly renewing DHCP lease, causing problems for Princeton IT


I think anyone posting "first" and saying nothing else should have their ip banned. Back on topic: is this something that a firmware update could fix?

Short memories at TiPb. It was Princeton that claimed there were DHCP issues with iPhones and iPod Touchs back in 2008. Much ado at the time. Princeton blamed Apple, same old, same old. Turned out it was a problem with Princeton's own network. Deja vu.

@smarty Grow up stup. The only network problems I had with my ipad is with verizon's network at my gf. It let's you stay on for an hour at a time and it bumps you off then you have to sign back on. It's not the ipad with the problem thought. Cause it does the same thing with her laptop, my laptop, my iPhone, her bold. Case in point the big v sucks.

I think I may be seeing a related issue. If I leave my iPad locked for a few hours and then pick it up and use safari then it won't receive data. It shows as being connected to my network, with a strong signal, but just cannot receive data. If I turn Wifi off and then on again in settings then it works just fine, presumably because it renews the lease.

I'm not surprised. My 3GS craps out on the wireless here and there and no it's not my router.

Most will not see this issue, but many will now blame it. DHCP renewal should be an easy fix if it is indeed Apple's issue. My money is on Princeton having network issues.
Note - wireless connectivity is not likely DHCP related people... don't blame one thing on the other. Upgrade or move your router so it actually covers areas you use your iPad in and move on.

My stupid ipad loses the wifi everytime I unlock it or if I don't touch it for a while!!! Apple better fix this.... I already memorize my stupid password from my modem....

My stupid iPad can't get a wireless signal when I'm 300' away from my access point. Access point says good to 200'. Apple better fix this! :rolls eyes: Nothing to do with DHCP.

If Princeton were using a proper DHCP server it would determine if the IP was still in use before re-issuing it (via an ARP packet).
It would not give out that IP to anyone else.
Its not uncommon to have occasional IP usurpation on a network, its been around since the Pleistocene, and most DHCP servers will whine about it in the log but deal with it just fine.
If this happens to you at home, put a reservation in your router for your iPad's mac address, and problem will be solved. It will always get that IP, and no one else will.
I'm sure this will be an easy fix for Apple in the next software load, but I promise you no one will leave their iPad idle for the three months it will take for Apple to push an update.

I go to Devry University (insert joke) here in Orlando. They just got a new wireless system, Bluesocket of all things. My iTouch can get on the network just fine but my iPad just refuses to, eve after buying the bluesoket app from the app store. Another issue I have sometimes is that safari shuts down on it's own, or refreshes an open page on it's own

Publishing this article will only do a few things:

  1. Give confused iPad bashers something more to whine about
  2. Give iPad owners who don't understand DHCP something to blame
  3. Give idiot corporate or educational security departments just another reason to block Apple products
  4. Panic a few newby network admins who don't know how to set up their DHCP leases correctly
  5. Waste more Princeton network administrators time when they should be going to class to learn something useful

I go to the University of Georgia and I'm having the same type problems they are having at Princeton. I've talked to the OIT folks and they say there is a system wide iPad problem. I have no problems with my iPhone, but the iPad has only worked once (the first time) because of the DHCP problem. It's really frustrating. I hope it is fixed soon.

If they would set their lease periods longer than most people stay connected this problem would pretty well disappear by itself.
One or two day leases should do. Even College kids sleep sometime.

I had the same problem last night, Rajjh. My iPad had a strong signal but could not access the internet. I turned off the wifi, then turned it back on and it worked.

In short another workaround is to set up a static IP address on tour Ipad. Then add a "reservation" in the DHCP section of your router. This will tell the router not to assign the particular ip address you assigned to your Ipad to any other device on your network.

These things are hell!! on single subnet (LAN) they don't get a new IP from DHCP, instead use one that was issued in the past and create static noise!!! these things suck!!

I work at a state university in the midwest and we have similar problems with the ipads. We have about 60+ right now that are "excluded" from our network for not releasing/renewing their IP properly. What we're seeing here is that it is 100% an apple problem with how apple's dhcp is implemented. it has nothing to do with our dhcp server, and it has nothing to do with our wireless deployment.

I'm and IT architect and perform extensive testing with all sorts of hardware and software systems (SAN, networks, handhelds, tablets, mobile, unix, linux, windows, etc...). There is a problem with the iPad. One issue I have noticed is that the iPad maintains IP Address information from a recently disconnected network and does not properly renew a DHCP lease on a new network. I have seen this going from a home network, to a corporate network, or vice versa....I have also seen this going from a home network to a public hotspot.
I ran a sniffer on the iPad...and what the iPad is actually doing, is requesting an address from a recently disconnected DHCP server (different network address, and not trying to acquire a new address from the new DHCP server). It requests a 192.168.x.x. address from a 172.16.0.x server. The new server assigns a new address...but the iPad still uses its old address and settings.
This is truly frustrating.

If I leave my ipad's wifi on for more then about 30 minutes, my home internet goes to a crashing halt except on my ipad. my xbox 360 will constantly connect and reconnect to xbox live and my computer is moving slower then my grandma.
If I turn wifi off on the ipad, I get internet back up and its fine. sometimes I have to reset my router to fix it truely

Ever since introducing iPad, iTouch, and Windows 7 on home laptop we have continuous IP address conflict issues. Not sure if it is all tied together, but it is very frustrating. Especially today when I was working from my laptop and had the iPad in the same room and couldn't have both on the wireless.

Ya there is wifi issue in apple ipad it create problem in connecting with the WIFI and also not showing good signal even if ipad is closer to router.but in laptop there is no issue like this,so better to buy laptop..

It is the iPads fault. I have been having the same issues on my iPad and MacBook pro on stanfords network. It is beyond frustrating, I have to constantly renew the dhcp lease every 2 mins in order for them to get Internet connection

Yes, there is a problem with DHCP. After months using a Static IP address on my iPad 1, it lost all communication. I decided to go with DHCP and it would not receive a leased IP address. I even ensured that my iPad was registered with my cable box and it still could not receive an IP address. This is not good!

hey guys heres two solutions:
1) go to settings ---> wireless__> click on your network on the list---> renew DHCP lease towards the bottom should work, sometimes takes two times
2) change the DHCP lease duration on your wireless router

they are basically pieces of crap. Steve Jobs final joke. Mine has so many DHCP problems that it's comical to even try to use the thing as more than a frisbee

Yes i have, I have no idea what to do, my Ipad seems to work here and there while I am at the office. At home I don't have a problem, yet here (the office) i can't seem to get online. I have no idea what to do????

Yes i have, I have no idea what to do, my Ipad seems to work here and there while I am at the office. At home I don't have a problem, yet here (the office) i can't seem to get online. I have no idea what to do????