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DHCP claims out of leases, but console says otherwise.

Posted on 2005-04-28
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Last Modified: 2010-04-13
I am experiencing the same symptoms as found in this question:

http://www.experts-exchange.com/Operating_Systems/Win2000/Q_21296430.html

Win2K SBS.  DHCP says it's out of leases, but when I look at active leases, only a handful are there.  I have tried restarting the DHCP server service and refreshing the console - to no avail.  The lease time is set to the default 8 days.  Scope size is 51, only 8 leases are listed.  There are no reservations or exclusions.

An interesting thing I do see is that BOOTP is enabled, though I'm not sure why.  There aren't any BOOTP images or options set.

Any idea where I can see these used-up leases and clean house?
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Question by:ckratsch
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LVL 14

Author Comment

by:ckratsch
ID: 13886951
Update, I checked the reverse lookup zone in DNS, and it seems that these leases may have been taken up during a domain migration.  Even with that information, there are still a number of leases wholly unaccounted for.
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Expert Comment

by:tonyteri
ID: 13888382
lower the lease time to 1 day
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by:ckratsch
ID: 13888580
Lease time is kind of beside the point here.  I am 100% certain, based on my checking of the reverse lookup zone, that those lost leases were handed out plenty more than 8 days ago.  Those leases should have expired a long while back.  The issue at hand is that DHCP says all 51 IPs in the scope are leased, but the part of the DHCP console which displays leases only shows 8.
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harleyjd earned 1500 total points
ID: 13892316
Quick fix - stop the DHCP servce, delete the dhcp.mdb file from the system32\dhcp then restart the service. This will flush the table, but it won't give you any idea why it broke.

You can also reconcile the scope. This may show you what MAC addresses are tied to what IP. I had a photocopier that took 65 adresses once. Reconcile (right click the scope) Verify then reconcile... Then delete the dhcp.mdb file as above...

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by:ckratsch
ID: 13893404
harleyjd, I'll give that a try, but it won't be until the next time I'm at that client site.  Hope you can be patient for a bit?
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Expert Comment

by:jeroenlemaire
ID: 13893545
it depends on how long your leases remain active.
i've had to maintain a system from another company a while ago, which had it's DHCP to save it's leases for 5 months... (way too long) this was because they wanted to remember the IP-adresses... I advised them to use fixed IP-adresses instead of dynamic IP's...

If you'd set your leases to 1 day, your problem would be solved...
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by:ckratsch
ID: 13893892
The DHCP lease time is currently set to 8 days, which is the default configuration if I recall correctly.  I'm not sure I understand how changing the lease time from 8 days to 1 day will drastically change anything.  If the lease time was set to 500 days, then that would make sense.  Can you elucidate?
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Expert Comment

by:jeroenlemaire
ID: 13893922
it depends on how much 'foreign' machines you get into your network...
Than switching from 1 day to 8 days will do a whole lot for you...

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by:harleyjd
ID: 13893945
I doubt it will change a thing - you have something taking leases without your authorisation or a corrupt database. Setting a different lease time will not help at all...

I'm happy to wait until you get a second look at it...

FWIW - A PC with an 8 day lease time will still test it's lease every time it boots, or connects to the network, and will always retry the lease after HALF the lease time is up.

If t were truly a foreign machine, you'd see the lease, and the MAC address in the leases table...

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by:ckratsch
ID: 13896519
There aren't foreign machines on this network.  It's a small office, and they don't get visitors often.  Even if they did, I should see the leases.  I'm definitely leaning towards a corrupt database.  Hopefully I'll get back to this site next week.  Thanks for the input.
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by:ckratsch
ID: 13937755
Doesn't look like I'm getting back there this week.  I haven't forgotten - just haven't been able to get back there to effect repair yet.  Moderator: thanks for your patience in not 'abandoning' this question.
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by:harleyjd
ID: 13941082
Questions don't officially get abandoned for 21 days, so don't sweat it...
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by:ckratsch
ID: 14087102
Okay, I'm back on site.  harleyjd, I followed your instruction with the dhcp.mdb file - and now it says there are 51 leases in use, with no leases listed under Address Leases.  I put the old dhcp.mdb file back, so that users already on the network would continue to receive addresses for the time being.

Then I got to thinking ... the scope thinks all of its addresses are in use.  The little blue exclamation point icon is on the scope.  Why don't I delete this scope and recreate it?

That worked.  Must have been some corruption with the scope itself, and not the lease table.  harleyjd, I'm still awarding you the points for providing some very valuable information.
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by:ckratsch
ID: 14088005
Bah, it's still acting funny.  It is handing out leases, as displayed by the server statistics, but not displaying them in the Address Leases list.  (Well, it displays one, but no others.)  I'm just going to shift DHCP services over to another device.
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Expert Comment

by:jeroenlemaire
ID: 14088087
how many client access licences do you have with your SBS?
Could it be that it is limited, and thus you only receive a limited number of IP's?
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Author Comment

by:ckratsch
ID: 14088126
No, it's like this:

DHCP scope of 51 (.100 to .150)
Address Leases part of DHCP console only shows a small number of leases in use.
Statistics of DHCP server show 51 leases in use.
Events in event log indicate that all DHCP leases are in use.
DHCP does not hand out addresses to new computers on the network.
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Expert Comment

by:jeroenlemaire
ID: 14088140
how many machines do you connect, and how long is your lease-time set?
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by:ckratsch
ID: 14088658
Please reread the thread, and try to understand that it has nothing to do with the lease time, or legitimate IP leases.  If it was just a simple configuration issue, I would not have posted a question here at all, let alone a 500 pointer.

In any event, it's water under the bridge now.  A different device is now serving DHCP successfully.  I know I haven't reached the technical answer to my question, but I have reached the practical answer.  And that satisfies me, hence my awarding points to the person who provided me with the most valuable information.

Thanks for your concern and attention.  This case is closed.
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Expert Comment

by:david_reaves
ID: 15032468
I've seen a similar problem...I can temporarily recover the addresses by doing a reconcile, then verifying. After a restart of the DHCP service then the errant IPs show in the lease listing and can be deleted manually.  The interesting thing is that this doesn't affect every scope on the server. See the currenly open question below for more details:

http://www.experts-exchange.com/Networking/Microsoft_Network/Q_21585139.html

Wierd!  
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