The first Apple iPhones are showing up in our US network. They seem to find the wireless network and acquire a DHCP address pretty easily. Some people are already using them with our email system. It is only a matter of time before questions start coming to us in the IT support group. What do we need to watch out for and is there any way to filter iPhones by their DHCP requests and block them from the network?

When joining the wireless network, iPhones can cause broadcast problems in networks that forward unicast ARP packets back into the wireless network, since an iPhone may send such a network request to see if it can still find the last network gateway that it was connected to.

This same behaviour can make it difficult for the iPhone to acquire a valid IP address in networks that require MAC address registration prior to obtaining a routable IP address through DHCP. You can force an iPhone to release its current DHCP address by clicking the Release button in the DHCP panel under Settings->WiFi Networks in the DHCP panel for the current network. While you may be able to block iPhone DHCP requests by filtering on MAC addresses, doing so may block other Apple systems from your network as there seem to be at least some other types of Apple computers using Ethernet and wireless MAC addresses from the same hardware address block iPhones are known to use for their wireless addresses.

Other than making sure your wireless network doesn't forward unicast ARP packets back into the wireless network, there shouldn't be any real differences between supporting iPhones and Blackberries and Treos and PocketPCs. IPhone users in an Exchange environment can use their email but won't get all the task and calendar integration some of the others might.