D-Link DKVM-IP1 User Manual page 52

Above: Click on "Device Settings > Network" to enable TELNET and SSH access. Also
remember to click the relevant setting on the Serial Port Settings page (screenshot below).
2) Also, before accessing Telnet or SSH, click on Device Settings > Serial Port to
open the Serial Port Settings screen (see the screenshot below). Make sure
"Passthrough access to serial port via Telnet/SSH" is selected.
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