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Incorrect subnet mask

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6 replies

by basconi

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We recently moved from one lan system to another. On the previous lan we used subnet mask 255.0.0.0 and on the current system we use 255.255.0.0. The current system is using win 2k server. Ever since the cutover we have had a problem with some of our win98 PC that for some reason get the old subnet mask (255.0.0.0) in the IP Config and subsequently they can't log in until we do a winipcfg and the subnet mask is correctly change to 255.255.0.0 However later we can experience the same problem on same PC.

6 replies

by timwalsh

Couple of things to check:

Ensure the DHCP server has the correct subnet mask defined in its scope. In the Win2K DHCP implementation, once a scope has been created, the only way to change the subnet mask is to delete the scope and then recreate it with the correct subnet mask. I suspect this is probably your problem.

Ensure that there isn't a second DHCP server available with the incorrect subnet mask defined.

by joseph moore

Providing the DHCP scope is correct, then try this. There is a known problem of sending static routes in the DHCP info (using the 033 code). You need to send static routes in pairs; sending an odd number can cause subnet assignment problems.
Technet article Q261489 talks about this:
http://support.microsoft.com/default.aspx?scid=kb;en-us;Q261489
(please remove any spaces)

This may not be the fix to your problem, but it is something to check.

hope this helps

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