If your Untangle is serving DHCP, you can set any of the assigned IP addresses to a static assignment. To do this, go to Config > Network > DHCP Server. On the left side of the screen is a box labelled "Static DHCP Entries". Click Add, you will need to enter the device's MAC address along with the intended IP address.
On the right side of the screen are the current DHCP assigned IP addresses. You can make any of these statically assigned by clicking the Add Static button to the right of the entry. Keep in mind, if your Untangle server is not serving DHCP, set static IP addresses will not get applied. You would instead want to do this on your DHCP server or the client machine itself.Follow