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my DHCP causes conflicts

Posted on 2003-11-24
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Last Modified: 2010-04-13
hi all,

my questions are:
1) i am using a windows 2000  DHCP server on my network! now it is causing the IP conflict.how this can be resolved? ; i have given a second class  IP scope or i have only 200 PCs connected at time otherwise i could assume it is caused by the luck of free IP

2)when installing windows 2000 advanced server clusters, Is it necessary to separate the Private cluster connection and the public cluster connection when both nodes are connected to a high speed LAN? i am asking this question because First i want to go for this technology but my two HP proliants Servers has one NIC each; second i really don't have much knowledge on windows Clusters

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Question by:winklez
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by:dschwartzer
ID: 9811704

1) This problem can exist if some computers on your subnet have static IPs, while others DHCP. It it really is your network, you can first of all release all assigned leases, disable the scope, then ip-scan the subnet to receive the list of assigned/answering addresses.
When you have this list, you can add them to the exclustion scope of the DHCP server. Reenable the scope.

d
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by:Roly_Dee
ID: 9812000
As a short-term fix, you should also enable "conflict detection" on the DHCP server. In the DHCP console, right-click the server, Properties, then Advanced. Set the number of pings: one should be enough, but maybe more if you serve a busy or WAN environment.

This will check an IP address before issuing it to a DHCP client by pinging it. If the address responds, then it is in use, and the DHCP server will record it as a BAD_ADDRESS in the active lease listing. After a few days you should have a list of these static addresses to follow up.
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by:winklez
ID: 9824441
Dschwartzer told to release all asigned leases on the DHCP server; how this can be done? u mean using IPCONFIG /release command? what about IP-SCAN?
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Author Comment

by:winklez
ID: 9824486
then what can u say about

when installing windows 2000 advanced server clusters, Is it necessary to separate the Private cluster connection and the public cluster connection when both nodes are connected to a high speed LAN? i am asking this question because First i want to go for this technology but my two proliants Servers has one NIC each; second i really don't have much knowledge on windows Clusters



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by:dschwartzer
ID: 9824567
You can release the leased from the DHCP server console - I don't hace one in front of me now, but as far as I remember, in the Address Leases section you'll see the active leases - which you can release by right clicking and selecting -> release (if my memory doesn't fail me).

As for the IP scan, you can either use Roly_Dee's suggestion, or try any of the free tools on the internet - the first one that the search returned was this:
http://www.ks-soft.net/ip-tools.eng/
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Roly_Dee earned 100 total points
ID: 9824774
Looking in the DHCP console within Active Leases, you have the option to 'Delete' a lease, but this doesn't force the client to release it. This only deletes the server's record of the lease. The client has use of the IP address until the lease expires.
The IPCONFIG /RELEASE is the proper way to release the lease, but the command only affects the PC it is run on i.e. you would have to visit each PC to release it's IP address.

So, to force all your clients to obtain new valid addresses (instead of renewing their existing IPs) you should do the following:
- enable "conflict detection" (as above)
- delete all of the leases from DHCP Active Leases (at the end of the day)
- visit the consoles of any PC that remains on overnight, and do "IPCONFIG /RELEASE" then "IPCONFIG /RENEW" at the console. This ensures they get valid IP addresses.

In the morning, all the PCs will obtain new valid IPs as they boot up.

PS I think your cluster will be fine using just one NIC per server, but might get a better response by posting a separate question for that one :-)
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