Recently ran into an issue with the iDRAC 7 remote access controller in a Dell PowerEdge T620. After updating the firmware from 1.35.35 to 1.56.55, I could no longer log in. After entering a valid user name and password, the web interface would start to load and then kick me right back to the login screen. I was logging in at the time using the IPv4 address of the iDRAC. Switching to using the DNS name of the iDRAC allowed me to log in. It turns out that Dell recommends clearing the cache in your browser whenever you make a major update to the iDRAC firmware. Sure enough, once I cleared the cache, I was able to log in again using the IPv4 address.