Just a heads-up: I just realized the syntax of the /etc/nsmb.conf file has changed in Sierra:
The entries of "smb_neg=smb1_only" and "smb_neg=smb2_only" are offically gone.
The only thing I see that resembles this entry is "protocol_vers_map" (manpage says "Bitmap of SMB Versions that are enabled" clear as mud!)
After testing I can confirm that:
"protocol_vers_map=2" sets SMB Protocol 2
"protocol_vers_map=1" sets SMB Protocol 1
This link was (slightly) helpful to me: http://www.gossamer-threads.com/lists/netapp/toasters/15969
