About SMB2 and SMB3 settings
SMB2 and SMB3 are under Optimization > Protocols: SMB2/3.
SMB2/3 settings
Enable SMB2 Optimization and Enable SMB3 Optimization performs latency optimization in addition to existing bandwidth optimization. These optimizations include cross-connection caching, read-ahead, write-behind, and batch prediction among several other techniques to ensure low-latency transfers. The appliance maintains data integrity, and the client always receives data directly from the servers. SMB2 is enabled by default; SMB3 is not. Configure on client-side and server-side appliances.
Enable DFS Optimization enables optimization for Distributed File System (DFS) file shares. Configure on the client-side appliances.
SMB Down Negotiation
None disables the attempt to negotiate the CIFS session down to SMB1.
SMB2 and SMB3 to SMB1 optimizes connections that are successfully negotiated down to SMB1 according to the CIFS (SMB1) settings . Configure on client-side appliances.
The appliance bypasses down-negotiation when the client or the server is configured to use only SMB2 or SMB3, or the client has already established such a connection with the server. Down-negotiation can fail if the client only supports SMB2 or if it bypasses negotiation because the system determines that the server supports SMB2. When down-negotiation fails, bandwidth optimization is not affected.