On the test, I will use the D-Link DES-1210-28/ME rev.B2 switch with firmware 6.07.B002.
Download the new firmware for DES-1210-28 / ME for the necessary revision from the official site
http://forum.dlink.ru/viewtopic.php?f=2&t=92700&sid=04ae57db59e0b60948ad8e76ecbbe0db
At the time of this writing, I downloaded the version rev.B2 v6.07.B072.
After downloading, put the firmware file on the TFTP server.
If you want to see how to start the TFTP server in my articles:
Starting a TFTP server in Windows
Installing and Configuring a TFTP Server in Ubuntu
Now we connect to the switch via telnet or console cable and execute a command that shows the revision and firmware version of the switch:
show switch
Run the command that will download the firmware to the switch from the TFTP server:
download firmware_fromTFTP 192.168.1.2 DES-1210-28-B2-6-07-B072-ALL.hex
Run the reboot command so that the switch boots up with a new firmware:
reboot
Is done. After updating the firmware, the switch settings have not changed.