MIB overlapping enables you to shadow MIBs that are implemented in subagents. For instance, you might want to implement the system group and snmp from MIB-II locally in your master agent, and delegate all other requests concerning MIB-II to a legacy SNMP agent implementing MIB-II. You do this as described in To Shadow Overlapping MIBs.
Run the mibgen tool to generate an implementation of MIB-II
Instrument the system group and snmp group as shown in the basic SNMP agent example in “Creating an SNMP Agent”
Register your generated MIB with the OIDs of both the system group, 126.96.36.199.2.1, and snmp group, 188.8.131.52.184.108.40.206
Create an SnmpProxy object proxying your legacy MIB-II agent, and register that proxy for the root OID of MIB-II