I have been battling this issue on my 35 node Windows 2000 with various Win 9x client network for over a year and it’s driving me crazy. No one I talk to has an answer or has ever seen it before.
When some clients try to renew their leases, for some reason the subnet mask goes from 255.255.255.0 to 255.255.0.0 or 255.0.0.0 and the PC will not connect to its network resources even though it has a valid IP address (the address pool is 192.168.0.110 – 192.168.0.250).
This happened over threedifferent DHCP servers (WinNT 4.0, FreeBSD, Win 2K) We are using a Cisco Catalyst 3500 Series XL switch that I suspect may be playing at least some role in the problem. Most of the NICs are Kinston KNE 100, but there are a smattering of other NICs that are affected as well. Most of the affected clients are running Windows 98 SE but a few are still Windows 95.
