SSH RSA keys must be <=2047 bits

For iDRAC6 to accept SSH key authorization, the key must be RSA<=2047 bits, or DSA. You may need to create a new SSH key just for that.

To create an RSA key that is 2047 bits long, and store it in drac and drac.pub:

ssh-keygen -t rsa -b 2047 -f drac

Apparently DSA, as implemented in OpenSSH, is considered weaker, so please use RSA. Sources: 1 2