DHCP released leases go to new computers too soon

Discussion in 'Server Networking' started by rschatz, Aug 17, 2007.

  1. rschatz

    rschatz Guest

    I recently noticed that my computers get a lease and use it for the day and
    then when they shut down release it. That's normal. Then, the next day,
    someone else gets the IP that machine had been using. Our lease times are set
    to about 2 weeks. The DHCP server is Windows 2003.
    In the past those IPs would not be given to someone new so that when the
    first computer connected again it could get the same IP that it had before.
    This way, computers tended to always have the same IP. By the way, the PCs
    are Windows XP.
    The problem with this is that WINS seems to not be releasing the registered
    name; so, I can ping the name of a computer that is off and it might respond
    because some other computer now has the IP that WINS has registered with the
    name. Also, if I use sp_who with SQL 2000 server, it might show a connection
    that belonged to one computer yesterday, but now even though SQL shows one
    name, it is actually a different computer. This seems to be because the
    connection to SQL is not being terminated even though a client computer may
    be turned off. So, it keeps the name and when a computer with the same IP
    connects, it seems to think it is the same computer. Any ideas? How can I get
    DHCP to give the same IP always to the same PC? Is it because the PC must ask
    for it and for some reason it is not?
    rschatz, Aug 17, 2007
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  2. Hello,

    Do you have the option "002 Microsoft Release DHCP on shutdown" on your DHCP

    If you want to be sure to never change IP, you can make reservation based on
    mac. So your computers will never change it's IP. Not possible on large
    network anyway...
    Mathieu CHATEAU, Aug 17, 2007
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  3. rschatz

    rschatz Guest

    In the scope options? No. I don't have it there and don't see anything like
    that anywhere else either. Thanks for the suggestion. And, no, I don't want
    to try to use reservations. That's not practical in this case.
    rschatz, Aug 17, 2007
  4. Can you check again the lease duration ?
    By default, windows will try to use again the previous leasing if it's still
    It will ping the default gateway to check for ip validity. Is it possible to
    ping your gateway ?
    Mathieu CHATEAU, Aug 17, 2007
  5. rschatz

    rschatz Guest

    Oui. I can ping it from everywhere. The lease is 15 days. Most of the
    expirations in that area of the building are for Sept. 1, for example.
    rschatz, Aug 17, 2007
  6. Do you have many scope / multi scope / more than one dhcp server ?
    Mathieu CHATEAU, Aug 17, 2007
  7. rschatz

    rschatz Guest

    Indeed. I have two DHCP servers that have similar scopes, but not the same
    There are about 37 scopes configured on each server. They're all just
    regular scopes.
    rschatz, Aug 17, 2007
  8. Strange, based on this, your workstation should renew their lease:

    Microsoft DHCP supports local storage, allowing clients to store DHCP
    information on their own hard disks. Local storage is useful because when
    the client system starts, it first attempts to renew the lease of the same
    IP address. Local storage also means that a client can be shut down and
    restarted using its previously leased address and configuration, even if the
    DHCP server is unreachable or offline at the time the client computer is
    restarted. Local storage also enables the ability to perform IP

    Does your computer get a new lease from another dhcp server ?
    If you issue an ipconfig /all, the lease period is 15 days ?

    Is your DHCP server stopped/start during night ?
    Mathieu CHATEAU, Aug 17, 2007
  9. rschatz

    rschatz Guest

    Does your computer get a new lease from another dhcp server ?
    They keep getting their leases from the same server. The server is not
    restarting. The DHCP server shows 15 day leases and my computer shows 15 days.
    rschatz, Aug 17, 2007
  10. just to be sure, workstation are 2000 and XP ?

    So you start, have a lease for 15 days, reboot, then you get a new ip ?
    If it's the case, that's not the default behavior, so we will have to digg
    the config to catch what is not by default
    Mathieu CHATEAU, Aug 17, 2007
  11. rschatz

    rschatz Guest

    Correct, actually, I think they're all XP, though I can't swear to that. I
    could tell by looking at the DHCP log that one computer in particular that I
    was interested in would get a different IP each day. Yes, there must be
    something messed on these computers. It could be all of them because an image
    was used to setup all these workstations. Here's an example from the DHCP log:
    Friday (today):
    So, computerA had, but no one has leased that today. Instead it
    stole which was computerB's address. The DHCP server shouldn't give
    that up anyway, I thought. So, the questions are: why does the computer not
    ask for the same IP from the same server and why does the server give up that
    address instead of giving up one of the other hundreds from the pool that
    haven't yet been assigned? Now that I think about it, the problem must be
    from the server. I'm going to try to find time to do a packet capture and see
    if the PC is asking for an IP and just not getting it.
    Thanks for your help so far.
    rschatz, Aug 17, 2007
  12. 12,08/16/07,14:24:06,Release,,computerA,000D56F5B77A,

    This is strange, should not release.
    Is it laptop ?
    If they are unplugged (but stayed on, like going to a meeting with it), XP
    will fail to ping and will go to autoconfigure
    Mathieu CHATEAU, Aug 17, 2007
  13. rschatz

    rschatz Guest

    Ok, after doing some sniffing, it looks like we have a couple of DHCP relays
    in the mix here too. Now I'm thinking the problem has to do with some of this
    Cisco equipment, routers or whatever. Hmmm
    rschatz, Aug 17, 2007
  14. rschatz

    rschatz Guest

    Oh, that's when the person leaves at the end of the day and shuts their
    computer down. They are desktop computers that don't move around.
    rschatz, Aug 17, 2007
  15. Ok.
    You may built a fresh windows, without using your master.
    Then you will know if it's the infrastructure or the master's workstation.
    Mathieu CHATEAU, Aug 18, 2007
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