Many users are not aware that a recent change has been made to the default password setting of new Nutanix nodes. Specifically, the default password for the IPMI interface is now the serial number of the node itself (using capital letters). Please note that the node serial number is different from the block serial number. You can find more information regarding this change as per the Common BMC and IPMI Utilities and Examples Knowledge Base article.
Also, if you desire to change the IPMI password, you can do so using the IPMI management utility located within the file system of the operating system running on the node. Further, you can even change the password, without having an operating system installed/running, by using the utility from a bootable DOS environment. You can find more information regarding this within the Changing the IPMI Password section of the NX Series Hardware Administration Guide.