Complete the following procedure to add secondary authentication on NetScaler 10.5 when primary is already configured:
Open NetScaler Gateway virtual server.
Click the plus sign (+) besides Authentication.
Choose the Policy type (for example, RADIUS).
Choose Authentication type as Secondary.
Select BIND.
Specify Name of Authentication policy.
Specify IP address of server.
Choose a saved expression to use (for example, ns_true).
Select Create.