In order to fetch the printer attributes, iPrint has incorporated the feature enhancement of secure communication through IPP on port 443 between the iPrint gateway and printers. To accomplish this feature, the iPrint gateway by default communicates with printers through IPP.
If the printer is not supporting IPP or if the communication between the iPrint gateway and printers through IPP fails then the printer's attributes are retrieved using SNMP. See, Modifying the Printer’s Gateway Load Commands.
Beginning with iPrint Appliance 23.4, you must use the product upgrade channel for updating both the iPrint Appliance patches and the appliance OS. See, Section 6.4, Updating to iPrint Appliance 23.4 through Product Upgrade Channel.