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DHCP issues

Posted on 2006-11-01
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Last Modified: 2010-04-18
I have a 2003 standard DC with DHCP service running.  My subnet mask is 255.255.255.0.  The problem is that some of my machines are coming up with a subnet mask of 255.255.0.0.  I've been looking at my other servers to see if DHCP services are runnung. Nothing has come up.  I also stopped my DHCP server and rebooted my workstation on the domain and it wasn't assigned IP address so I know that I only have one DHCP server.  Does anyone have a recomendation where I can look further into this issue.  I need to find out where this mask is coming from

Thank you
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Question by:jkaminsky
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SeanUK777 earned 250 total points
ID: 17850564
check your network for a bright spark, that may have installed a VM, unintentionally connected to your LAN running DHCP..

I have a few in my team..
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by:jkaminsky
ID: 17850608
Virtual Machine???
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by:SeanUK777
ID: 17850708
some people set up Virtual Machines on there workstations to get familair with Server operations etc etc..

One of my techs, did this that, but mimic our setup, and as a result we had a rogue DHCP server on our network..

You could run a netdiag from the command prompt..

Maybe you can see which machine is supplying the IP Address..
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by:inbarasan
ID: 17850786
In the system you get the SB 255.255.0.0 , Just do the following
Give IPconfig/all

It will show the DHCP server IP. Check whether it is same DHCP which you are referring. With this you may find problematic DHCP server on your Network
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by:jkaminsky
ID: 17851808
inbarasan

I found a machine with the 255.255.0.0 and it is pointing to my DHCP server which is my DC.  I didn't think of that I will keep trying
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by:sushibilly
ID: 17856025
What IP address are you getting. Is it in the correct scope?
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by:SeanUK777
ID: 17856226
Are all your IP addresses for your client machines assigned by your DHCP server..

On the DHCP server, goto the address leases, and check if the machine with the mask of 255.255.0.0 is appearing there..

I
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by:jkaminsky
ID: 17883412
It ended up being the dell switches have a know issue my network guy was able to fix this problem

Thank you to all of your for your help and support
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