always fetch the same ip addresses everytime they boot
 

How can I make a dhcp server that will fetch the same ip addresses even they(workstations) reboot??

You can configure DHCP server with MAC address of workstation, and than it will always take this same IP.

A dhcp server assigns IP addresses to workstations.
After the general dhcp server configuration...it;s something like this

host agri2 {
hardware ethernet 00:1a:4d:2c:59:2f;
fixed-address 192.168.1.11;
}