Common Internet File Service (CIFS) is the successor to the server message block (SMB) protocol. CIFS is the primary protocol used by Windows systems for file sharing.
CIFS uses UDP ports 137 and 138, and TCP ports 139 and 445. Your storage system sends and receives data on these ports while providing CIFS service. If it is a member of an Active Directory domain, your storage system must also make outbound connections destined for DNS and Kerberos.
Starting with Data ONTAP 7.3.1, CIFS over IPv6 is supported. CIFS over IPv6 uses only port 445. Ports 137, 138, and 139 are used by NetBIOS, which does not support IPv6.
CIFS is required for Windows file service. You can disable CIFS by issuing the cifs terminate command on your storage system console.