Non-Scoped DHCP Reservations

Joshua 1 Reputation point
2020-10-27T18:26:22.79+00:00

When creating a new DHCP reservation, the wrong number was entered and it created a reservation out of scope. So now I can't see it in the GUI to delete it, and my Powershell skills seem to be lacking in finding reservations out of scope. Any suggestions?

For reference, our scopes range from 10.0.8.255-10.0.16.255, when inputting the reservation, someone put in 10.0.3.100 instead of 10.0.13.100. How do I find that address (10.0.3.100) and delete it? It's prohibiting me from being able to create a reservation for this machine.

Thanks for any help you all can give.

Windows DHCP
Windows DHCP
Windows: A family of Microsoft operating systems that run across personal computers, tablets, laptops, phones, internet of things devices, self-contained mixed reality headsets, large collaboration screens, and other devices.DHCP: Dynamic Host Configuration Protocol (DHCP). A communications protocol that lets network administrators manage centrally and automate the assignment of Internet Protocol (IP) addresses in an organization's network.
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  1. Leon Laude 85,651 Reputation points
    2020-10-27T18:36:12.823+00:00

    Hi @Joshua ,

    So the invalid scope that was created doesn't show in the DHCP console? If you go to the scope, then expand it and head to the Reservations tab, do you see it there?

    Otherwise you could try deleting it with the PowerShell command below: 

    Remove-DhcpServerv4Reservation -ComputerName "DHCPServer.domain.com" -ScopeId 10.0.3.100

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    (If the reply was helpful please don't forget to upvote or accept as answer, thank you)

    Best regards,
    Leon

  2. Candy Luo 12,656 Reputation points Microsoft Vendor
    2020-10-28T02:27:35.557+00:00

    Hi ,

    What's the OS version of your DHCP server? As far as I know, from server 2008 R2 and later, DHCP server will check if the reservation belongs to Address Pool. You cannot add a reservation outside of the configured range. If we add a reservation that is outside of the distribution range of a scope, we will receive the following warning message :

    The specified DHCP client is not a reserved client.

    35566-image.png

    For your reference:

    You cannot add a DHCP reservation that is outside of the scope distribution range in Windows Server 2008 R2

    Anymore, you might try the following command to free the MAC address for use: 

    run netsh dhcp server scope SCOPENAME delete reservedip RESERVEDIP erroneousMAC (erroneousMAC=MAC unable to add)

    As the picture below:

    35613-1.png

    For more details, you can refer to the following link:

    DHCP Reservations fail with "Specified address is not available" and more!

    Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

    Hope this can help you.

    Best Regards,

    Candy

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