Readers speculate on Duke University’s iPhone problem

By John Cox, NetworkWorld.com, 07/17/07

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The iPhone Wi-Fi puzzle continues to baffle both the Duke University IT team and readers at Networkworld.com and other tech sites.

As reported Monday, a few iPhones on the campus-wide wireless LAN occasionally and unpredictably are triggering floods of Address Resolution Protocol (ARP) requests, as many as 18,000 per second. The flood overwhelms groups of Cisco WLAN access points, anywhere from a dozen to 30 at a time, taking them offline for 10-15 minutes or so.

So far, the Duke troubleshooters are pretty sure it is the iPhone, and not the university’s Cisco infrastructure, that is causing the disruptions. The phones are calling for the MAC address of an invalid router, and in effect, won’t shut up.

The speculation is that the flood may be triggered when the iPhone user moves from one part of the campus WLAN to another, disconnecting along the way. For some reason, when the iPhone tries to re-associate at the new location, it may be calling for an address that previously worked: the wireless router in the user’s home. It’s not a valid device on the Duke WLAN, so the iPhone inexplicably keeps jabbering for it.

But there’s no want of other explanations from tech-savvy (and some perhaps not so tech-savvy) readers on several sites and listservs. You can contribute to the networkworld.com discussion here, and cast your vote on who’s to blame in our online poll. Early Tuesday evening, Apple was leading with 54%, followed by Duke’s IT group, with 24%.

For a few Network World readers, there’s no question who’s to blame. It’s Apple. Unless it’s Cisco.

“Jeez, sounds like these guys at Apple are having their hands full when it comes to their new phone. I personally wouldn't buy the piece of crap!” wrote 'hpv.'

Another reader, more reasonably, observed that, “The article doesn't specify if this is a single device malfunctioning, or if it is a defect in the iPhone itself. Reviewing the logs should help to narrow that a bit and if it can be isolated to a single device or two.”

In fact, as of Monday, July 16, Duke’s traffic analysis indicated that at least two separate iPhones had triggered ARP floods. IT staff talked with the school's iPhone users, who didn’t seem to have done anything out of the ordinary, except that the users of the two separate iPhones had moved from one building to another. It was after this second connection was made to the WLAN that the flood occurred. That still leaves open the question of whether it’s a malfunction in one or two iPhones or a genuine iPhone bug, or no bug at all but something exposing a flaw or misconfiguration in Duke’s net.

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