after upgrading netscaler from version 8.1 to version 9.0 we had to create the Access Gateway Virtual Server.
het error was protocol error
after that you have to set the user limit for your license
The interface command identifies either the hardware interface or the VLAN interface that will be configured. Once in interface configuration mode, you can assign physical interfaces to switchports and enable them (turn them on) or you can assign names and security levels to VLAN interfaces.