DHCP Server

DHCP server
Hello, we have a DHCP server in our LAN and there are about 300 clients in our LAN. We added some computers to our LAN but they could not give IP from DHCP, what is the reason? Thank you for your help.....

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The ability of pc’s to pull ip’s from a DHCP server depends on a couple of things.  First the pc must be configured to receive a dynamically assigned address.  Go to the pc’s adapter settings, check properties under IPV4 and make sure “obtain ip address automatically” is selected.  Once that is the case you need to make sure that your DHCP server has a large enough pool of addresses.  For example if you are handing out addresses in the /24 network you have a maximum of 254 usable addresses.  You don’t need to use the whole network as your pool, you could use only addresses .1 -.100 for example.  If however, your needs exceed the size of the pool you need to expand your pool.  A class B network, with a 24 bit mask again gives you 254 addresses which would not meet your needs.  You would need to expand the size of the pool of your available addresses.  Move from a /24 to a /23 for example which would give you 510 usable addresses. 



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  • TomLiotta
    what is the reason?   Without an error message or event identifier of some kind, we can't know why it's not working. One reasonable possibility is that the DHCP server was configured to supply a range of addresses, and the range is now filled. You'll need to update your DHCP server to cover a larger range if that is the problem.   If it's not the problem, then more information is needed.   Tom
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  • Gabe9527
    Are the new machines in a seperate segment? Is there firewalls in the way?Are the NIC card properties set to used DHCP?Is there enough IP addresses in the scope?Are these machines trying to use a 169.x.x.x? this means the NIC card has tried and assigned itself an IP address?As Tom has said more info please
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  • jinteik
    and what is the scope allocated for your machines? if lets say you set 300 u got 320, then 20 pc wont get ip
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  • James Murray
    I think everyone here is on the same page with DHCP.  When you mention 300 clients recieving DHCP, I assume you mean some type of user workstation?I'm curious how you are setting up your printers, servers and static devices.  I'm also curious if your DHCP is letting go of IP addresses.  There is always a redflag when someone says 300 of anything when talking about a standard subnet.You didn't mention that you have multiple DHCP segments or a non-standard scope (i.e. more than 254 IP addresses per segment)  I am wondering if your environment is highly mobile and you've never had more than 200 users on the network at a time?  Is the lease on your IP numbers very short?  Normally I would have multiple scopes setup.  I wonder if you have a backup DHCP server that is backing up the original and it's been taking part of the load and it has failed?  There are so many things it could be, it's difficult to answer the question without more details on the environment.
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  • orangehat
    Sounds like a home work question.
    2,130 pointsBadges:

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