Restrict clients to a specific Remote Desktop Task Server
You can restrict clients to take instructions only from a specified Task Server. To do so, you use the command-line to add a plist key entry to a preference file on each client. The plist key value is the Network ID (MAC address) of the en0 interface of the Task Server.
To execute the command-line tool, you can:
- Use an SSH session to the client computer 
- Use Terminal on the client computer 
- Use the Send UNIX Command from Remote Desktop 
Execute the command-line tool as root or using sudo. If you use the Send UNIX Command as root, sudo isn’t necessary.
- In the Terminal app  , enter the following command to create the plist entry: , enter the following command to create the plist entry:- sudo defaults write /Library/Preferences/com.apple.ARDAgent ServerWhiteList -array <en0>- Replace en0 with the en0 Network ID of the Task Server (no spaces, dashes, or other punctuation in it). 
- Enter the following command to add additional Task Servers to the plist entry: - sudo defaults write /Library/Preferences/com.apple.ARDAgent ServerWhiteList -array-add <en0>- Replace en0 with the en0 Network ID of the Task Server.