Princeton publishes report detailing iPad DHCP issues

Tue, Apr 20, 2010


Princeton University recently documented some problematic wireless issues they’ve encountered on campus due to the growing number of iPads.

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.

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.

After Princeton’s routers notice a device repeatedly running afoul of DHCP protocol, the device is subsequently blocked from the campus network, which if you own an offending iPad, is pretty bad news. According to the report, Princeton officials observed that nearly half of all iPads using the Princeton network experienced the issue described above. After a little bit of investigating, Princeton narrowed the problem down to the iPhone OS 3.2, and promptly reported the issue to Apple on April 7th.

Notably, Princeton points out that the DHCP issue is entirely separate from other reports which have complained about poor wi-fi reception and connectivity.

After discovering the issue, Princeton advised iPad owners not to connect to campus networks, but yesterday they published a possible workaround to the issue. “Beginning April¬†19¬† (now that we have a possible workaround), when an individual iPad malfunctions,” the report notes, “we contact the owner to advise him or her of the problem and refer the owner to the workaround. If the same iPad malfunctions a second time, we block that device and contact the owner again.”

With the 3G iPad still not available, wi-fi is the only way current iPad owners can access the Internet. Hopefully a software fix will be coming soon.


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