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  1. #1
    Newbie
    Join Date
    Aug 2014
    Posts
    3

    Default Clearing DHCP leases

    How does one go about Clearing DHCP leases Untangle. We are running V10, it should be as simple as on Windows Server. CLICK DELETE.

    We have dozens of client PC's, Phones, and other devices that its not as simple as release or renewing a lease, as well as being impractical or impossible to do so.
    Not too mention, we have multiple locations and I have to have the ability managed remotely.

    Without having to SSH into untangle, is there a way to clear a DHCP client lease from within the GUI?

  2. #2
    Untangler jcoffin's Avatar
    Join Date
    Aug 2008
    Location
    Sunnyvale, CA
    Posts
    9,665

    Default

    Quote Originally Posted by wolfbarkley View Post
    How does one go about Clearing DHCP leases Untangle. We are running V10, it should be as simple as on Windows Server. CLICK DELETE.
    That action on the Windows server DHCP service does not renew the IP on the client. That only puts the IP in the pool again, the client has to request a new IP before it is changed on the client. It works the same on Untangle. Once the lease expires on the client, the client will ask for an IP from the server and get the new IP.

    http://technet.microsoft.com/en-us/l...=ws.10%29.aspx

    6. Force the client with the existing lease to give it up. At the command prompt on the client computer, type ipconfig /release.
    Last edited by jcoffin; 08-28-2014 at 03:36 AM.
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  3. #3
    Untangler
    Join Date
    Jul 2014
    Posts
    35

    Default Clearing DHCP leases

    I had a computer on the network. Had a static IP address ending in .1.10
    Reformatted and reinstalled the OS. Configured with a different NetBIOS name and static IP address .1.11.
    Plugged it into the network. From that moment, it was recognized on the network, when pinging the old NetBIOS name and and it returned an address .1.147. No way could I convince the other computers that this was a different machine.
    The computer that replaced the original and was given the original's name, could no longer be found on the network, except by IP address. Nothing I could do could delete the old, wrong, address lease. Tried disabling DHCP and rebooting the UT server - no joy.
    I read that I could use SSH to delete a file containing the leases, but that can't be done unless you are at the console - I had no way to do that, because there is no monitor available on the client site.
    Having SSH disabled by default is likely a good security idea, but being unable to enable it, even when you have the admin password is just stupid. Also, those DHCP leases should disappear after they haven't been used for a while. Other DHCP servers allow the manual removal of a lease. While you may not need to use it often, it can be handy for such situations.
    In case someone else is having this problem, instead of getting all angry with UT (like I did), try this (worked for me):
    Create a static IP entry in the DHCP page for the server/computer/printer - use the MAC address and give it the IP address you want. At the computer, ipconfig /flushdns, and everything should work fine again, even though the wrong DHCP lease is still there.
    So, you now have a static IP address for the computer in question, AND you have a wrong DHCP address lease for the same unit. For some reason, the static IP address you configured will take precedence.
    There should be a way to manually release a leased address, in case something goes astray. There isn't, unless you happen to have SSH access, which most people wouldn't set up or know how to use. (Again, like me.)
    Untangle is great, but it's also a pain in the butt at time...




    Quote Originally Posted by jcoffin View Post
    That action on the Windows server DHCP service does not renew the IP on the client. That only puts the IP in the pool again, the client has to request a new IP before it is changed on the client. It works the same on Untangle. Once the lease expires on the client, the client will ask for an IP from the server and get the new IP.

    http://technet.microsoft.com/en-us/l...=ws.10%29.aspx

    6. Force the client with the existing lease to give it up. At the command prompt on the client computer, type ipconfig /release.

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