dhcp lease time problem with iphones

dhcp lease time problem with iphones
dhcp lease time problem with iphones
2012-11-16 17:37:01
Region : Sweden

Model : TD-W8961ND

Hardware Version : V1

Firmware Version : 1.0.0 Build 111125 Rel.28195

ISP : Telia


Hi!
I am experiencing a problem with DHCP lease time.

Iphones that are connecting to my router (TD-W8961ND v1) are getting a lease time (expire time in the dhcp lease table) of 90 days.

This causes the dhcp table to fill up, since the router is serving at a gym, where people connect their iphones to the wireless network of TD-W8961ND.

The dhcp lease time is set to 86400 seconds (1 day), and the regular PC clients are respecting the lease time, but the iphones seem to have their own idea about what is a good lease time.

Currently the dhcp pool is 240 addresses big, but it fills up anyway. Maybe I should just set static leases on all PC-clients, but that's only a workaround, not a real solution.

Any hints? I tried setting something called "renewaltime" through the telnet interface.

See attached image for the dhcp table



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Re:dhcp lease time problem with iphones
2012-11-16 18:33:12
It seems that your problem is caused by those Iphones.
And I also found a link where there is a discussion about the DHCP lease problem caused by ipad/iphone OS 3.2 in Princeton University:
http://www.zdnet.com/blog/hardware/ipadiphone-os-3-2-dhcp-issues-surface/8062
What is the OS version of those iphones in your case ?
Maybe you can turn to Apple support for advices.
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Re:dhcp lease time problem with iphones
2012-11-16 18:44:31
Thanks for the reply, but I already read up on that Princeton article, and as it says (though I might have missed something in the full Princeton article):

The iPad owner is often unaware of any problem, Nevertheless, it is an issue because it can interfere with service to other devices. Once the iPad has allowed its DHCP lease to expire, the DHCP server may lease the same IP address to another client.


This is not the case for us. The problem is that the lease has a significantly higher lease time than what is set on the router (90 days instead of 1 day).

Maybe I just need to read up on the dhcp protocol and sniff some iphone network traffic, but it seems a lot easier to just set static ip:s for the regular computers.

Since it's so many different iphone belonging to the guests of the gym, we have no way of telling the iOS version or iphone version, and no way of controlling them either.

Would be interesting to see how other dhcp servers act when an iphone connects.
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