Cisco UCS C220 M5 ESXI Version OEM Downgrade from 7.0 to 6.5

[Taiga2022]

Hello All, 

We are planning to Migrate our CUCM 10.5 VM from old hardware to new C220 M5 hardware. 

The device is already installed with ESXI 7.0 and OEM Licensed. While we are checking the CUCM compatibilities with ESXI, CUCM 10.5 cannot run on ESXI 7.0. We need to downgrade the ESXI 7.0 to ESXI 6.5. 

I'm not sure how we can achieve that. If we have the separate license key, then I could just reimage the ESXI but since this one is OEM Licensed, I'm worry that I might lose the license if I did that.

Any advices or comment are welcome.

Thank you in advance.

[Kirk J]

There is no 'downgrade', only a fresh install.  The datastore/file system created in 7, will likely not be readable via 6.5 so you will likely have to copy off your guestVM files to another location prior to reinstalling an unsupported version of ESXi 6.5.

Unfortunately it looks like you will be in a completely unsupported scenario (esxi 6.5 went end of support years ago), as is CUCM 10.5.

Hope this isn't for production.

Kirk...