UCSM KVM Console Displays Black Screen

Over the past several weeks, I have been standing up new hardware in order to expand a cloud infrastructure. During this process, I was tasked with standing up new UCS hardware. I configured the static IP addresses on the N6K devices, configured the firmware to the appropriate versions and created the appropriate service profiles. The next step was to install the base operating systems.

With PXE in place, I opened the KVM console from UCSM and waited for the server to power on. Once the server was powered on, I saw the Cisco splash screen as expected. The problem was once the the system posted, only a black screen was seen on the console. It appeared the blade was functioning and no error messages were seen on UCSM, however the screen remained blank 30 minutes later. I attempted to open the console on several other blades and to my surprise they are experienced that same problem.

When I plugged a physical KVM directly into the server to check the console, the screen displayed as expected. What was going on?

As I had mentioned, this was new UCS hardware and as such it came with a newer firmware version (1.4.1m) then what other UCS systems were running (1.3.1n). During the initial configuration of the new hardware, the firmware was downgraded on UCSM and the N6K prior to the chassis being added (this was done so a configuration import could be performed). In addition, the service profiles were configured to downgrade the BIOS and a couple other hardware firmware levels. Once the chassis were added, the IO modules were downloaded to stay compatible with the N6K devices automatically.

The only thing that was not downgraded was the CIMC (i.e. KVM) firmware. This meant the system was running firmware 1.3.1n everywhere except on the CIMC, which was running 1.4.1m. Since this was the only difference I could find between the new UCS hardware and the existing, I assumed the CIMC firmware was not backwards compatible and downgraded it to 1.3.1n. Upon doing so, the KVM console worked as expected.

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