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DHCP issue

Our DHCP server is giving errors in Event Viewer is giving messages that our scope of 192.168.1.0 is 87 percent ful with only 16 IP addresses remaining.  With all of the servers and printers that are static and the clients that are dynamic, the total does not seem to be close to the 255 limit.  How can this number be more accurately attained so that we do no run into an issue for growth?
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regsamp
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regsamp
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3 Solutions
 
xrokCommented:
Look at DHCP Range
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regsampAuthor Commented:
The range is 192.168.1. to 192.168.254 but there is just not that many pieces of equipment to reach near that total.  
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Chris DentPowerShell DeveloperCommented:

Hi,

What do you have the Lease Time set to? If you have a lot of different devices coming on and off the network and a long lease time then addresses will never be released back into the pool.

HTH

Chris
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cobubaCommented:
First look at the subnet mask that the DHCP server is handing out to verrify that it is 255.255.255.0
also verify that the DHCP server is not handing out address to a nearby LAN or WLAN for that matter

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ViRoyCommented:

its warning you early before it gets to be a critical issue. even with static addresses defined, if they are in the same scope, they will be counted.

however, are you saying that theres no way your network has that many IP addresses assigned?
if so you may need to check the DHCP server and see how long the client leases are before being released. they could be so high that alot of the addresses are reserved even though the clients are not powered on all the time.
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regsampAuthor Commented:
We have recently had some new devices come on that I can account for taking about six static IP addresses but this has been the first new added equipment in the last few months or so.  I believe that the lease time is set for 10 days.  How can this be confirmed?  
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regsampAuthor Commented:
The servers are static and they will be counted as they are in the same scope.  The DHCP is handing out 255.255.255.0 and it yes there should be no way that there is that many IP addresses assigned.  The client leases are set for a long period as the lease expiration dates on most of the clients are out to 4/29 so how can I check what the default time is set for the clients in DHCP?  
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Chris DentPowerShell DeveloperCommented:

Windows DHCP?

If it is...

Open up DHCP Manager, select your scope and open the Properties. Then Lease Duration for DHCP clients is what you need.
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xrokCommented:
set a lease time to 1 day
No reason to keep lease time that long

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regsampAuthor Commented:
Thank you Chris-Dent.  It is set for 8 days and when I go to the Scope and then display statistics, it is saying total addresses 125 and in use is 109, leaving 16 (12%) left.  How can this be as the range is 192.168.1.1 to 192.168.1.254?
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Chris DentPowerShell DeveloperCommented:

Do you have any exclusions setup in the scope options?
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Chris DentPowerShell DeveloperCommented:

Sorry, under the Address Pool rather than Scope Options.
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Gary GordonCommented:
I concur with those above who suspect that the problem is lease time.  Reduce the DHCP lease time and use ipconfig/release and ipconfig/renew from a C prompt on trouble clients to referesh their DHCP information.
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regsampAuthor Commented:
The only exlusion range is from 192.168.1.1 to 192.168.1.129.
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Chris DentPowerShell DeveloperCommented:

That would do it, it's cutting your IP range in half.

If you don't need all that excluded from distribution I'd delete that one and make a smaller exclusion range.

Remember to exclude things like your server addresses from the scope.
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xrokCommented:
>it is saying total addresses 125 and in use is 109, leaving 16 (12%) left
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xrokCommented:
If you don't have 109 equipment, then set a lease time to 1 day
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xrokCommented:
or reduced the  exlusion range
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regsampAuthor Commented:
I do not know why someone had set that up to include that many as we certainly do not have that many static IPS.  If the excluded list is deleted then the devices with static IPS must absolutely be included in the new excluded list or even static devices run the risk of a lease, correct?
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Chris DentPowerShell DeveloperCommented:

Correct, although you can reserve single IP addresses if necessary to deal with static devices being too wide-spread over the range.
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regsampAuthor Commented:
Seems logical.  What about the lease period here, we seem to have opinions of one day instead of the current setting.  To short or somewhere in between?  
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Chris DentPowerShell DeveloperCommented:

When you say "run the risk of a lease" I kind of assumed you meant something like: a DHCP client getting assigned an address that conflicts with a static IP on a different device.
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Chris DentPowerShell DeveloperCommented:

Well it depends on the turn-over of devices on your network really.

Generally speaking the lease time is fine at 8 days. But if you have a high equipment turnover (for whatever reason) then a shorter lease time is much more appropriate.

Equally, if you prefer each device to keep the same IP then a long, or even unlimited, lease time works better.

Hope that helps.

Chris
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regsampAuthor Commented:
We have a small equipment turnover rate and I prefer the devices to have the same IP for a resonable time so somewhere between 1 to 8 seems to be the guideline.  Thank you Chris.  
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Chris DentPowerShell DeveloperCommented:

No problem... happy to help :)
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