Can't find the option -domain-workgroup when create cifs server

I create a two node netapp simulater. I'd like to specify domain-workgroup when create or modify cifs server. But can't find this option. After create cifs, can find this option in -fields.

fsqe-2nc1::vserver*> version
NetApp Release 9.7: Thu Jan 09 11:10:19 UTC 2020

fsqe-2nc1::*> cifs modify -vserver vs1 -cifs-server ONTAP2-04A5 -domain FSQE04A5.REDHAT.COM -domain-workgroup rhts

Error: invalid argument "-domain-workgroup

fsqe-2nc1::vserver*> cifs show -vserver vs1 -fields domain-workgroup
vserver domain-workgroup
------- ----------------
vs1 FSQE04A5REDHATC

I have two questions:

1. why need to specify domain option when mount cifs? That's the reason I want to modify the domain-workgoup

like this:

  mount //$ONTAPIP/cifs1 -o domain=FSQE04A5REDHATC,user=administrator,password=~Ocgxyz /mnt/cifsmp-ontap

But without 

2. How can I specify or  modify domain-workgoup?

Thanks.