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Subnet Mask

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by scopo

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I have a windows 2000 server on my class C network running DHCP. My clients about 50 machine are running win98. What is happening is that the client machine's subnet mask keeps changing from 255.255.255.0 to either 255.0.0.0 or 255.255.0.0. When this happen they cannot see other machines on the network and they receive a message that "no domain controller was available to validate the passowrd". what is causing this problem and how can I resolve it? I thought the problem was caused by my network class. I had a class A address with a class C subnet. But I have since changed to a straight class C and the problem is still occuring on some of the clients. Is this a problem with the clients or a settings on the DHCP Server?
Thank you foryour assistance.

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by mr. ezekial transistor

Check what scope information your DHCP is providing those clients. Could there be a rougue DHCP server on the network? Do you have DHCP relay agents? Does the IP change when the subnet mask changes? Check the client DHCP leases and compare when theyexpire to when the subnet masks change. Try making the leases really short then watch the client and see what happens when it expires. Perhaps their lease expires, they go to renew it, can't communicate with the DHCP server for some reason and they are set to Obtain IP Address Automatically in the TCP/IP properties and they give themselves a 169.254.x.x with subnet mask of 255.255.0.0

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