This article, tells you how to restrict Cyberoam GUI access to certain IPs from LAN, so what to do, if you want to restrict to specific Public IPs from WAN.
Create a Host Group (named here as WAN IP Access Group) with list of Public IP addresses that you want to provide access, then create WAN-LOCAL access list to limit the access to Cyberoam’s WAN interface IP.
You also need to enable the appliance access via WAN.
