On the test I will use the D-Link DGS-3612 switch with firmware 2.84.B48 and Boot PROM: 1.10-B09.
I will update to version 3.00.B42.
I will describe the update procedure:
1) Download the new firmware from the official site (there they are referred to as DGS-3600)
After downloading, put the firmware file on the TFTP server.
If you want to see how to run the TFTP server in my other articles:
Starting a TFTP server in Windows
Installing and Configuring a TFTP Server in Ubuntu
2) Connect to the switch via telnet or console cable and see what version of firmware is installed on the switch:
show switch show boot_file
3) Make a backup copy of the configuration just in case:
upload cfg_toTFTP 192.168.1.2 dest_file 3612.cfg
4) Upload the firmware to the switch with the TFTP server command (the firmware file needs to be renamed shorter, since the switch file I sometimes didn’t accept the switch):
download firmware_fromTFTP 192.168.1.2 src_file RUN3.HAD dest_file unit 1 C:\ RUN3.HAD boot_up
5) The last step is to reboot the switch, enter the command and press “y” for the reboot agreement:
After updating the firmware, the switch settings remained unchanged.
I updated the firmware remotely via telnet.