In order to monitor a different subnet with the ARP component of the network services, first install the network services on a host in the subnet which needs to be monitored:
Once completed, install the WinPcap drivers which are required by the ARP daemon. The WinPcap drivers can either be downloaded from the web (https://www.winpcap.org/) or found in the resources sub directory of the EventSentry installation directory (e.g. C:\Program Files (x86)\EventSentry\resources\winpcap_4_1_3.exe).
Once that has been installed, you can then configure the "ARP DAEMON" and then restart the Network Service on that machine.