you can restart the DELL iDRAC over ssh when you cannot connect over the html web management page with
racadm racreset soft
To do so, connect over SSH to the iDRAC and run the racreset
# ssh hostname-idrac -l root root@hostname-idrac's password: /admin1-> racadm racreset soft RAC reset operation initiated successfully. It may take a few minutes for the RAC to come online again. /admin1-> Connection to hostname-idrac closed by remote host. Connection to hostname-idrac closed.
Now wait some minutes until iDRAC is restarted and it’s available again over both ssh and html web.