We are using /24s in our vlan pools and have 15 minute lease times. This is due to the number of transient devices (e.g., iphones and ipods) that hop online for barely a minute and then go back to sleep and disassociate. We had issues where these would exhaust our dhcp pools, even with these short lease times. So, for us, it's not a matter of one device eating multiple addresses.
========== Ryan Holland Network Engineer, Wireless Office of the Chief Information Officer The Ohio State University 614-292-9906 holland....@osu.edu On Apr 19, 2010, at 1:29 PM, Johnson, Neil M wrote: > What size subnets are you using for wireless ? > > In order to use our public /21’s efficiently we have our lease time set to 10 > MINUTES. > > -Neil > > -- > Neil Johnson > Network Engineer > Information Technology Services > The University of Iowa > Work: 319 384-0938 > Mobile: 319 540-2081 > Fax: 319 355-2618 > E-mail: neil-john...@uiowa.edu > > From: The EDUCAUSE Wireless Issues Constituent Group Listserv > [mailto:wireless-...@listserv.educause.edu] On Behalf Of Caroline Owens > Sent: Monday, April 19, 2010 12:22 PM > To: WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU > Subject: Re: [WIRELESS-LAN] Princeton determines cause of an iPad problem > > Admittedly, that sounds pretty cool.... Do you have a particular type of DHCP > in mind that support that? I don't run the dhcp server, but if there was a > way to do what you're suggesting, I would present that solution to the person > that does.... > > On 4/19/2010 1:15 PM, Jeffrey Sessler wrote: > Even with multiple smaller subnets, you can prevent IP address hogging as > long as the DHCP server provides a mechanism to remove client leases from the > other pool at the point it hands out a lease to the same device in the new > one. > > Jeff > > >>> Caroline Owens <ow...@sju.edu> 4/19/2010 9:45 AM >>> > They could create longer lease times and not have an issue if they have only > one flat wireless subnet. > > But if they have several smaller subnets, these longer leases could really > add up if a device acquires an IP address from each subnet within a small > window of time. You wouldn't want a device hogging two or three other IP > addresses on subnets that it's not currently using. On a college campus with > students that roam all over and have iPhones, this situation isn't out of the > realm of the possible..... > > Caroline Owens > Networking and Telecommunications > Saint Joseph's University > > On 4/19/2010 11:27 AM, Jeffrey Sessler wrote: > It would seem that Princeton could temporarily (or permanently) avoid the > problem, and thus all the media hype and blocking of the iPads, by simply > increasing their DHCP lease time from their stated 1-3 hour time to something > more reasonable. Unless your base of devices include a large number of > drive-bys (devices seen only once and never again), I'm not sure that a lease > time of 1-3 hours will result in better DHCP IP address pool use than say a > lease time of 24 hours. > > > We toyed with extremely short leases years ago but found they resulted it > various device anomalies. We now run with lease times of at least 24 hours > and our average IP address consumption changed very little. > > > Jeff > > > "Zeller, Tom S" 04/18/10 8:54 PM >>> > > http://www.net.princeton.edu/announcements/ipad-iphoneos32-stops-renewing-le > ase-keeps-using-IP-address.html > > iPad gets DHCP lease. If iPad happens to be sleeping during the renewal > time it awakens and uses the IP number forever (until shut down of unit or > WiFi or going out of range) > > Tom Zeller > Indiana University > > ********** > Participation and subscription information for this EDUCAUSE Constituent > Group discussion list can be found at http://www.educause.edu/groups/. > > ********** > Participation and subscription information for this EDUCAUSE Constituent > Group discussion list can be found at http://www.educause.edu/groups/. > > > > ********** Participation and subscription information for this EDUCAUSE > Constituent Group discussion list can be found > athttp://www.educause.edu/groups/. ********** Participation and subscription > information for this EDUCAUSE Constituent Group discussion list can be found > at http://www.educause.edu/groups/. > ********** Participation and subscription information for this EDUCAUSE > Constituent Group discussion list can be found > athttp://www.educause.edu/groups/. > > Spam > Not spam > Forget previous vote > ********** Participation and subscription information for this EDUCAUSE > Constituent Group discussion list can be found at > http://www.educause.edu/groups/. > ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.
