Use the Unit Identifier field within the Modbus TCP Server section of the SCADAPack TCP/IP tab to specify the Modbus/TCP Unit Address of the SCADAPack E outstation.
For a SCADAPack E outstation to operate as a Modbus/TCP server, you have to select the Modbus/TCP (Server) service within the Enabled TCP/IP Services section of the SCADAPack TCP/IP tab (see Enable TCP/IP Services), otherwise the setting of this field is ignored.