John,
I assume you've set the CIMC mode to "Shared LOM" correct? This will transport the CIMC communication via the LAN on Motherboard ports "shared" versus the "Dedicated Mode" which utilizes the out of band Management interfaces.
Once you've ensured that is correctly set, have you assigned a VLAN to the CIMC interface or is the CIMC IP within the same IP subnet?
[I see you have a TAC case open for this also. I'll let you go through the process with TAC and then I'll update the thread closing the loop.]
Regards,
Robert