This is a rare occurrence which can happen from time to time. This can either be caused by a bug in the Firmware or in some extreme cases bad Electricity being fed to the server. The following is what you can do in order to resuscitate your Dell iDRAC 6/7 card.
1) If the iDRAC web interface is inaccessible, you can try to remote into the iDRAC by using SSH Port 22(You can use Putty to do this). Once logged in, you can issue the following command
racadm racreset soft (This will do a soft reset of the iDRAC)
or
racadm racreset hard (Only use this if your iDRAC is not responding to the soft reset command)
2) If you have Dell OpenManage installed, you can use Dell OpenManage to reset the iDRAC to it’s default settings and you can then reconfigure the access IP again.
3) If you have tried all these steps above and you still cannot access your iDRAC, then you will need to shutdown your affected server and physically pull out the power plugs from the server. Then allow about 2 minutes for the residue power to drain from the server and once this is done, you plug the server back in and power it on. Once the server has powered on, try accessing the iDRAC.
4) If you have tried all these steps and you still cannot access the iDRAC interface, then the best option is to call Dell Support 🙁
I hope all of you find this useful!