After updating the iDRAC of my Dell PowerEdge r630 I had the problem that I could not connect to the webfrontend anymore.
The solution was that I set the DNS name that I use to access the iDRAC, so that the host header check does not fail, which blocks the connection.
You can read about this in the following article from Dell.
https://www.dell.com/support/kbdoc/en-us/000189996/idrac8-https-fqdn-connection-failures-on-2-81-81-81?lwp=rt