There is a way to change the CIMC ip via the APIC cli and you MIGHT be able to assign the IP (need to test), but in either way you need root access to the APIC and only TAC can logging as root. Without root access this is not possible without reboot.
If you reboot one APIC at a time to assign a CIMC IP address while maintaining the majority of the APIC up and running you should be able to manage and modify your ACI environment. You just need to make sure that before rebooting the next APIC they are all fully fit.
We don't have access to the CIMC interface and we can't even ping it. Interface is up and cabling is ok, but there's no input traffic. According to project manager this was working before. Can we or Cisco TAC check the current CIMC IPs somehow and check that configuration is correct? We have connectivity to the APIC management interface, only CIMC is not working.