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  • #2093228

    IP conflicts using DHCP


    by joemoran ·

    Gentlemen (and ladies),

    I’ve got a weird problem here that I would love to get some thoughts on.

    I’ve got an office here using a private C class IP range, and I’m assigning my clients addresses out of a DCHP scope.

    Every so often, some people get pop-up messages about IP conflicts. However, none of the classical problems exist here. I am not reserving addresses, there are no addresses assigned statically from inside the range, no exclusions, etc.

    It is all really straightforward. Myonly conclusion is that for some reason, DHCP is assigning the same address to more than one client simultaneously.

    When I go into the scope properties, all of the addresses that were double-assigned are listed as bad, and then I purge them, but it happens again and again.

    My DHCP lease is the standard 3 days. Any thoughts on what is going on here? It is driving me bonkers.



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    • #3869118

      IP conflicts using DHCP

      by gregory w. smith ·

      In reply to IP conflicts using DHCP

      If you “purge” the bad addresses, DHCP *will* reuse them as soon as it needs to, even though another device may still be hanging on to the address. What you should try is:
      Leave the bad addresses alone in the database (for now)
      For each one, ping the address. Determine which PC or other network device it is and do a release/renew from it. Only when there is nothing responding at the “bad” address should it be removed from the database.

      Alternately, stop the DCHP service momentarily and try a release/renew at a workstation. If it successfully renews, you may have a rogue DHCP server (Internet router, another NT server, etc.) When you renew, WINIPCFG (on a 9x client) will tell you the address of the server that assigned you the addressso you can hunt down the rogue and kill it.

    • #3869065

      IP conflicts using DHCP

      by avachon ·

      In reply to IP conflicts using DHCP

      Hi, information about active IP leases is stored in both the DHCP database and the registry of your machine running dhcp server. For many reasons, it’s possible for the info. stored in these two locations to become unsynchronized. The registry may show more than one IP addresses as leased while the DHCP database shows the same leases available. You can run a consistency check – running this lists inconsistent IP addresses and reconciles the state of the dhcp environment maintained by the registry. To reconcile:
      1. select active leases from the scope menu to display active leases
      2. Click reconcile. If databases are consistent, dhcp manager displays a message telling you that. If not consistent, it lists the inconsistent addresses. Alwaysrun this reconciliation procedure after a server crashes or when you restore dhcp databases. Reconcile operates on individual scopes so if you have multiple scopes, run reconcile individually for each scope. Hope this helps.

    • #3869031

      IP conflicts using DHCP

      by allan ·

      In reply to IP conflicts using DHCP

      If you have users with laptops, make sure that they shut down the machine before they disconnect the network cable.If they just pull the cable first the IP address isn’t released properly in the DHCP server.

    • #3869756

      IP conflicts using DHCP

      by joemoran ·

      In reply to IP conflicts using DHCP

      This question was closed by the author

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