In the event you have a Dell server where the iDRAC GUI is unresponsive, you can use the following telnet commands to perform power management functions:

/admin1/system1-> racadm serveraction hardreset
/admin1/system1-> racadm serveraction powerdown
/admin1/system1-> racadm serveraction powerup

When the operation is successful, you'll see the following response

Server power operation successful