#SNMP has various methods for authentication which is a way of proving you should have access to the query.
The story of AES authentication is a little sad. For AES-128, it's simple as RFC3826 added it and DES.
However, AES-192 and 256 were not added by the RFC and there are two standards; Cisco is IETF draft Blumenthal. The difference is only in the OIDs they use but if your sender uses one and receiver the other, it won't work.