@Bhav Just for clarity, do you have an isolated imaging network or are you trying to image on your business network?
If you have an isolated imaging network then you should have configured FOG to setup a dhcp server. The configuration will work for both bios and uefi computers.
If you plan to image on an existing business network, then your primary dhcp server needs to be configured to support pxe booting.
So lets start with how do you plan on imaging?
Second if you are planning on imaging using your business network, what device is your current dhcp server?