iOS7 DHCP IP address scopes being depleted

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iOS7 DHCP IP address scopes being depleted

I work for a large school district in Texas. We have a large deployment of iPads (10,000+) as well, we encourge BYOD.

Our district has recently updated to iOS7. We now are experiencing IP address scopes running out of IP's, 6000 per campus for students, 5 campuses. With some testing we found the iOS7 devices leave the network - IE: go to sleep mode or disassociate from wireless in some fashion, generally for just a short period, 1 hr or 2. Once the iOS7 devices rejoin the network they are not keeping their original IP address and allocated another IP thus in a days time depleting IP addresses.

Our DHCP lease times are set for 8 hours.

We have tested this with iOS6 devices and these devices leave and rejoin and retain their original IP address from the scope.

I was wondering if any other ISD or other enviroment with a large deployment of iOs devices have seen this problem?

Thanks

LB

iPad, iOS 7, DHCP IP Address problems

Posted on Oct 11, 2013 8:23 PM

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Answer 1

SAC13

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Oct 30, 2013 9:05 AM in response to LB_MISD

We are having this issue too at our College. We added 500 more addresses and in less than a minute they were consumed. We have also noticed devices with multiple IP addresses. One iPad had 4 IP addresses.

Have you heard about any fixes from Apple on the horizon? This issue has taken our wireless implementation to its knees.

Thanks,

SAC13

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Answer 2

LB_MISD Author

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Nov 1, 2013 7:03 AM in response to SAC13

SAC,

I have discussed this with our Apple engineer, he said to submit a support case....?

So, first let me tell what I have done so far to date.

I have to explain that we have Cisco wireless controllers, WiSM 2 (4 in total) in our 6500 chassis.

We use the Cisco Prime NCS to mangae all the controllers. Cisco ISE for AAA authentication and Microsoft DHCP and LDAP servers for Directory Services. All Schools have AP groups with their AP's in that specfic group.

But in short what I found that helped everything was re-booting all the Access Points on our controllers.

Monitored the the situation and seems to have cleared up. I hadn't rebooted them in while, since before the iOS 7 release.

BTW, We tried doing the same thing by adding more IP addresses,actually created entire new scopes with about 1000 addresses /22. Like you experienced, those were used in a matter of minutes! We realized that was not a fix. At first we thought.. Wow the kids are bringing a lot of devices from home onto the network.. but soon noticed the devices with several IP's for the same device.

So try rebooting all of your AP's if you can. let me know how it goes.

LB

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Answer 3

SAC13

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Nov 1, 2013 9:37 AM in response to LB_MISD

Thanks for the feedback LB. We Have Aruba for wireless, 2 controllers, also Microsoft DHCP and LDAP Directory Services.

Did you figure out why a reboot of the APs worked? I am not sure I understand how the reboot can help. If we reboot ours, we will need to schedule, so I won’t do that until next week where we can be around to watch it. Will let you know how we make out.

Thanks for your input.

SAC

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Answer 4

rccharles

Level 6

13,037 points

Nov 1, 2013 11:17 AM in response to LB_MISD

Could you try changing your lease time to less? One hour?

That way your access point would be forgetting the old ip address that the ipad was no longer using?

Please note this is a big guess on my part. I do not know the downside of this besides a little more network traffic.

go to sleep mode or disassociate from wireless in some fashion, generally for just a short period, 1 hr or 2.

does the device ( ipad ) know the lease period? ipad thinks... gone to sleep. maybe the lease has expired while i've been sleeping. don't want to use old address. maybe someone elase has address now. best to get a new address. shouldn't access point be sorting this out via MAC address?

All added addresses being used up is minutes is odd and bad.

I mean there is a button my Mac's ethernet window that say renew ip address.

Robert

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Answer 5

SAC13

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Nov 19, 2013 8:43 AM in response to rccharles

We were at 2 hours lease, and that seemed to keep our heads above water. We rebooted the wireless controllers which in turn reboots all of the access points. I was able to make it back to 4 hour leases, but when I tried to move up to 6 hours we choked again, so we stayed at 4 hours.

Although we are okay right now at 4 hours, that is not a solution to me. I should be able to have 8, 12 or 24 hour leases if we choose, so I am still searching for an answer why this all of a sudden started happening after iOS7 was released. I am thinking more along the lines of the differences between iOS6 and iOS7 and how they hold on to IP addresses. More research...

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Answer 6

3f3d37

Level 1

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Dec 1, 2013 9:25 PM in response to LB_MISD

Hi All,

Found this thread when searching for a solution to a similar dhcp problem on Friday.

I came across this issue when building a wireless env similar to LB_MISD. Although in my env I have a linux server for dhcp and have two pools (one for known and another for unknown clients). Ios 7 devices were actually making so many requests it caused the DHCP server to stall at times.

From the logs I noticed that I had problems with unknown clients but not with known clients ..... the difference - an assigned hostname in dhcp for the known clients.

IOS 7 seems to require a hostname be given to the client device with the rest of the dhcp offer. To get around this I added an extra line to the dhcp pool that send the clients mac address back as it's hostname. It does not appear to actually get used by anything but does seem to fix the problem.

"option host-name = concat ( binary-to-ascii (16, 8, ":", substring (hardware, 1, 6));"

I don't know what the equivalent config would be for a windows server or home router - although a workaround might be to grab the mac addresses of all the IOS 7 devices and reserve an address and create a hostname for each device --- a pain yes but at least the dhcp server may work for everyone else?

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