Regarding SMB/CIFS Monitor

What should be the "Service Name" while configuring SMB monitor on NAS server. And secondly i am getting error "Access denied" when F5 tries to connect to NAS to perform health monitor. I have entered the username and password , but not sure why it is taking AD as MYGROUP, so on the logs it displays the username entered as MYGROUP\user1 , whereas in my NAS server the account user1 is created as Local. Kindly help