A while back, I found that my iDRAC firmware was out of date. Being a good sysadmin, I downloaded the update and followed the instructions to perform the update via the iDRAC itself. Being a while back, I don't remember exactly what transpired but the update failed in one way or another. Upon rebooting the server, my fans were running full throttle and I was unable to connect to the iDRAC.

I did some sleuthing on the Internet and found another poor soul with a similar issue. His solution was to perform a recovery of the iDRAC via a serial connection to the iDRAC and a TFTP server to serve the firmware.

Source: https://buildingtents.com/2014/04/24/idrac6-recovery-through-tftp-and-serial/