iPhone/iPad using multiple DCHP ip address lease

Posted on 2012-08-17
Last Modified: 2012-08-20

When looking at my DHCP server lease log (e.g. the router's log - Asus RT-N12 v1.0.1.4), I find that many (if not all) iPhone and iPad on the network take multiple IP address leases and all on different MAC address.

The main issue with this is that the DHCP server lease range is completely used up. Yes, I can change the subnet address from class C to either B or A, but still, does anyone know why these devices use so many IP addresses (I've seen one with 15 IP addresses assigned to an iPad-2, with 6 more that were expired).

I have set the lease period to 7200 seconds (2 hours), but the expired IP address don't seem to really get released by the device.

Question by:rjjacques
    LVL 53

    Expert Comment

    The different MAC addresses part doesn't make sense. You can find the actual MAC address of the iPhone, iPod or Ipod in the general settings under Wi-Fi address, The device will also have a separate address for Bluetooth, but that should not matter.

    The only thing I can think of is that some of your users may be using connection sharing to share the wireless connection from their iPod, etc. to other devices. I can't think of any other explanation for multiple MAC addresses from one device.
    LVL 53

    Expert Comment

    How are you determining that different MAC addresses come from the same device? You may have other people poaching your connection.

    Author Comment

    Here's the DHCP lease log from the router. You can see the various MAC addresses and IP assignments

    I really don't have a way to know if the client device is setup for connection sharing (is this the default setting ?), though I cannot foresee an iPad having 14 other client devices given the physical environment of the the hotel room they are located into.

    Hope this helps

    PS: I was told once that this behavior is an Apple "feature/issue/bug", though I have not found any litterature to confirm this, and that those devices tend to suck up your network and use tricks to bypass the normal way of doing networking.
    LVL 53

    Accepted Solution

    You are misinterpreting the log. For instance, look at the lines:

    Thomass-iPhone  64:B9:E8:2D:10:EE   6019 secs
                                3C:36:3D:3E:DF:07   5997 secs

    These do not mean that both of these addresses belong to Thomass-iPhone.
    The first address does, but the second address belongs to a device that does not broadcast its name, and hence the name is shown as blank.

    You can find the manufacturer of the NIC that the MAC address belongs to using this link:

    This shows that the second MAC address in the list above, 3C:36:3D:3E:DF:07, belongs to a Nokia device (presumably a smart phone) and not to anything manufactured by Apple.
    LVL 53

    Expert Comment

    Whoever told you that this is an Apple trick is either malicious or grossly misinformed.
    LVL 17

    Expert Comment

    by:Sikhumbuzo Ntsada
    Apparently there is known flaw about the  some Apple devices where they will broadcast the MAC addresses of your previous hot spots/wireless connection they were successfully paired with.
    LVL 26

    Expert Comment

    "Broadcasting" the MAC address has nothing to do with "connecting from" the MAC address.
    You are indeed misinterpreting the log.  Each of those different MAC addresses belongs to a different device.  You have many more devices connecting to your network than you think you do.

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