IP conflict (DHCP assigned) when hibernating on home network

Discussion in 'Network Routers' started by David D., Jul 13, 2006.

  1. David D.

    David D. Guest

    I have been researching postings about IP conflicts using DHCP. Although
    there are tons of such postings, most have to do with mixing DHCP with
    static IPs, or with split-second timing problems, or with clearing IP
    conflicts after they have occurred.

    I suspect that my IP conflicts are related to leases expiring and IP
    addresses being reassigned while the original lessee is hibernating.

    This is a home network with a cable-modem and a router that serves as my
    DHCP server. There are no static IP addresses in the DHCP IP pool range.
    Computers in my house are typically hibernated rather than shut down, so
    that work in progress can be left open, and so that the computers power on

    I have had intermittent IP conflicts with my old, wired Linksys router. I
    eliminated that problem by setting the IP lease length to three years.

    My new router is a wireless Netgear, with both wired ports and wireless
    connections. This may complicate things a little for two reasons: (1) the
    Netgear router does not have a setting to allow one to change the IP lease
    length, and the lease length is pretty short, and (2) the same computer
    might have one wireless connection and one wired connection. I prefer to
    keep wireless disabled for increased security and higher bandwidth, but it
    is often convenient to use wireless.

    However, the problem still occurred with the old, wired-only router.

    My network is a mix of Windows XP, Windows 2000, and Linux-based appliances
    (a pocket print-server appliance and a TiVo).

    Will an expired IP lease be discovered on waking from hibernation? Could
    hibernation be the problem? Or is there some other issue that I should be
    looking at?

    - David
    David D., Jul 13, 2006
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  2. David D.

    Glen Guest

    Go into your router's setup and see if you can reserve each IP address for
    each computer. Tell the router the proffered IP for each computer. Usually
    done via the MAC code. It should be fairly obvious but if you need more help
    repost with the make model of router.
    Glen, Jul 13, 2006
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  3. David D.

    David D. Guest

    Thanks, Glen.

    I will take a look. I know that my router (Netgear WGR614) offers
    MAC-based security. I will look to see if it also has preferred IP by MAC

    I set up the router with WPA security. I do not know if I need to turn
    off WPA in order to use MAC security, but I will explore the related admin
    menus and let you know how I make out.

    I would still be interested in knowing the cause of my IP conflicts.
    Netgear tech support told me that I cannot get IP conflicts by hibernating
    computers, that the router will handle everything correctly. I am not
    convinced that that is the case. For example, what happens to Browser
    sessions that span the hibernation? I suggested a firmware upgrade to
    allow one to set the IP lease duration, in order to solve the IP conflict
    problem via a long lease. Their response was essentially that there is no

    - David
    David D., Jul 13, 2006
  4. David D.

    FedUp Guest

    On Thu, 13 Jul 2006 14:07:49 -0400, David D. wrote:

    In your power management settings ensure that your NIC is not powered off
    when your computer goes into hibernation. ll my computers retain network
    connectivity even when in hibernation mode.
    FedUp, Jul 13, 2006
  5. David D.

    Glen Guest

    When you start a computer it gets assigned an IP, eg from the
    router. When it hibernates it effectively shuts down. Windows as it was
    running is stored in the hibernating file. When another computer on the
    network starts up, the router, thinking the previous IP is now free (because
    the hibernating computer is effectively shut down) assignees to
    the computer just starting up. When the hibernating computer wakes up it
    already thinks it has the right to use because as far as its
    concerned it was given to it and it hasn't given it up. Hence the conflict.
    Glen, Jul 13, 2006
  6. David D.

    David D. Guest


    Thanks for the tip about the router setting for reserved IP address by
    MAC address.

    The Netgear WGR614's configuration menus are well designed. I did not
    even have to type in the MAC, IP and computer names. They were prefilled
    for me. All I needed to do was to click a radio button.

    David D., Jul 18, 2006
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