I have a Windows 2008 Server (Enterprise) (SP2) running as a domain controller, with a DNS and DHCP service. When a client requests an IP it get gets the ip ok, and the gateway, and DNS addresses ok, but gets the subnet mask as 255.255.255.1 (i don't get to see much of the network!). The DHCP has a simple scope of 10.195.2.100 to 10.195.2.195 (not that i have that number of machines!) whhich has a subnet mask of 255.255.255.0 There are no DHCP related messages in the events. Anyone one got any suggestions?

Hello, For further investigation, please help to collect: 1. IPconfig /all output from the problematic client. 2. Run the following command to get the DHCP full dump. net dhcp server dump>c:\dump.txt 3. Capture the network trace on the problematic client when request the IP lease from the DHCP server. Download the NetMon3.3 from the following link: http://www.microsoft.com/downloads/details.aspx?FamilyID=983b941d-06cb-4658-b7f6-3088333d062f&displaylang=en 1) Install the network monitor on the problematic client. 2) Start the capture and try to renew the IP address lease by "ipconfig /renew" 3) Once the issue is reproduced, stop the captures and save the network trace files. You can also send the trace log to me at v-mileli@microsoft.com for further investigation. If you have any questions or concerns, please do not hesitate to let me know.

logs sent as requested. regards.

Hello, Thanks for the update. Sorry for the late reply due to the Chinese New Year holiday. I have received logs at February 15. According to the IPconfig /all output and network trace, it seems that you have connected both NIC (Local Area Connection and Wireless Network Connection) to the same router (XX.XX.2.207). The subnet mask comes from the router which also acts as the DHCP server. Please understand that connecting more than 1 NIC to the same network (with same gateway) will result in network connectivity issues. Please double check the scope configuration on the router to verify whether 255.255.255.1 is set as subnet mask. If you have any questions or concerns, please do not hesitate to let us know.

The machine in question does indeed have two NIC's - a LAN and Wireless connection. They are both using XX.XX.2.207 (Windows 2008) as domain controller, DNS and DHCP server. The wireless connection is vis a wireless Access Point which is connected to the same LAN. There is a common gateway - a router connected to the broadband modem. How do people configure this situation? I have used this configuration previously with the same machine and have successfully worked within another domain (Windows 2000 based). The same problem occurs if i have only one NIC active (e.g. LAN connected with wireless disabled). I have other machines with a single NIC that are exhibiting the same subnet mask problem. The DHCP server is definitely configured for subnet mask of 255.255.255.0.

After spending a fair bit of time of this trying to work out what was happening i dropped the DHCP Scope and re-created it, and now everything is working fine. I would love to know why the original scope didn't work (it had work at one time).