This system name server is resolve Name->IP for RansNet devices to communicate with external systems via FQDN, such as mfusion server, or VPN gateway public FQDN/IP.
By default RansNet devices use google DNS (8.8.8.8, 8.8.4.4) as the name server. You can change it from the sytem menu.
Go to "Device MAC --> System" menu
The respective CLI is:
!ip name-server 8.8.8.8 8.8.4.4!