Many times we find the need to reserve IP addresses for specific purposes, this reservation is made through DHCP and most brands of modern routers let you do this configuration, as in the case of the router D-LINK model DIR 505, which allow us to reserve IP addresses, and assign the same IP address to the network device with the specified MAC address any time it requests an IP address. This activity is similar to the static IP configuration with the difference that the device should always make an IP address request from the router. The router will provide the device the same IP address every time. DHCP Reservations are helpful for server computers on the local network that are hosting applications such as Web and FTP. If you are going to use a computer just as a server it is needful toeither make a DHCP reservation or Static IP address.

In the strict sense, the DHCP reservation differs from the static IP  configuration in which the DHCP reservation is made on the router itself, instead, the static IP configuration set is done in the computer. In any case, the effect and applications are similar. This depends on the number of addresses available on the AP or router and this also can be configured within the same software.

There are three basic parameters to consider:

• Computer Name:   This is a free-assignment parameter and is given to the computer which is configured with a reserved IP address. This may help you keep track of which computers are assigned this way. Example: Movie Server.  
• IP Address: The LAN address that you want to reserve. You should have some care chosing this IP because it must be between the specified range given to the initial configuration of the router
• MAC Address: You can enter this parameter in two ways:
• Manually: in a shell command window, write ifconfig and the MAC address is HWaddr and is corresponding to your network adapter. If you are going to reserve for all the adapters of a PC, you must do this steps for every adapter, obviously, using a different IP Address for each single adapter.

Copy this code and paste in the MAC Address textbox.

Automatic: Using the cloning link/button built in web management of the router. In a D-link router this is 'Clone your PC's MAC Address'. Once you finished entering those parameters you can save the changes and maybe you would need to restart both, the computer and the router. 

Note: Please consider the fact of being carefully with IP assignment and to not repeat this for avoiding create network conflicts.