You cannot assign IP addresses to your client machines using DHCP after you install Hyper-V

Source: Microsoft Support

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After you install the Hyper-V role on Small Business Server (SBS) 2008, SBS will no longer be able to assign IP addresses to your client machines using DHCP.  Installing Hyper-V prevents DHCP from properly binding to your network adapter.

Adding the Hyper-V role to an SBS 2008 server is not supported. 

Uninstall the Hyper-V role from the SBS 2008 server and reboot.

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