DHCP scope IP's are being stolen by other VM's or switch ports etc. in the same network. Since, This is a flat network and any person who is spinning a VM is being served by my DHCP VM. So, I freed those IP's and again still being occupied instantaneously.
So, I have requested the network admin to create a seperate VLAN and sepearate subnet for my testing so that my DHCP IP's won't be grabbed by someone else 