If upon starting an SNMP session you see "Could not load MIB File" errors such as the one below:
Could not load MIB file 'CISCO-IF-EXTENSION-MIB.my'. Details: CISCO-IF-EXTENSION-MIB: Unknown SNMP data type: IfOperStatusReason (of node cieIfOperStatusCause).
The corresponding MIB need to be placed in the same directory or loaded beforehand.
iTest is indicating that this MIB is depending on another MIB which is not located in the same directory. Typically you can find which MIB needs to be included by looking at the Imports section and cross-referencing it with the error message. For example, the Imports section for the MIB mentioned in the error above shows:
The error iTest is reporting is indicating a problem with IfOperStatusReason. By examing the Imports we can see that this is dependent on the "CISCO-TC" MIB. Adding this MIB to the same directory resolved this issue.