If you are Ontap9.0, you can set it up without AD.
I got it work on my NetApp 8080 with Ontap9.0 version.
1) Create CIFS server via CLI
Cluster1::>vserver cifs create -vserver <SVM> -cifs-server <SVM> -workgroup <workgroup01>
2) set diag
3) Enable local users auth
Cluster1::>vserver cifs options modify –vserver <SVM> -is-local-auth-enabled true
Cluster1::>vserver cifs options modify –vserver <SVM> -is-local-users-and-groups-enabled true
3) Create your local user that will authenticate
Cluster1::>vserver cifs users-and-groups local-user create –vserver <SVM> -user-name <USER>
4) Create a CIFS LIF on the SVM (separate IP but can be in same subnet as NFS)
5) Create a CIFS share on the same volume as the NFS mount
6) Map to the CIFS share using the user from step 3. \\<LIF-IP-Address>\<CIFS-Share>