The VMan SNMP MIB file downloaded from Setup > Advanced Setup > SNMP Configuration > MIB cannot be imported to an SNMP manager.
The CA Spectrum SNMP manager is currently known to be affected by this issue.
The default Virtualization Manager MIB file contains several non-mandatory declarations. Because of the non-mandatory declarations, certain SNMP managers might not be able to import the MIB file.
Download the modified MIB file from the attachment of this article. This file does not contain non-mandatory declarations, and you will be able to import it to your SNMP manager.