I have a M610 iDRAC that stopped responding and no longer displays its configured ip address from the CMC. Swapping the Management Riser Board and changing slots did not help. Interestingly, I can even update the Idrac firmware from the OS level. The CMC and idrac are the newest levels.
The following works: Power On/OFF from the CMC, Updating the Firmware from the OS, blade server is fully functional on the network.
The following does not work: KVM, IDRAC network interface , assign/read the IP from the CMC, update software or get software inventory
With the iDrac and CMC being up to date and at the most current revision, then I would start with trying to perform a RACADM RACRESET on the idrac, then I would do a CMC Failover, if there is a redundant CMC to failover to. Perform those steps and then let me know if the functionality returns.