The restaurant separates network for staff from for guests. Devices of the restaurant are connected to the local access points which are networked with the Router, the local server is connected to a wifi transmitter in the system.
With this option, the restaurant should install the network as follows:

• Install 1 Modem directly connected to the provider's network line.
• Install 2 Routers connected to Modem, 1 Router for local use and 1 Router for the guest's use.
• The restaurant installs additional access points which connect with the local Router. 
• All of the staff's devices are connected with the access points, and the local server is connected to the local Router.
• All of the guests' devices are connected with the access points for guests.

Configure the network as follows:

• Assign IP address of access points (Wifi 1, Wifi 2, Wifi 3...) the same as IP address of the Router. View details here.
• Use another device which is directly connected to the local Router to assign an IP addres according to MAC address of the local server. View details here.