that the domain name MUST be in caps when connecting to the database.
db2 connect to SAMPLE user dbadmin@CF.IESECURITY.COM
I could not put the "using" and the password due to the password starts with a special character & which results in error.
I execute the above command and then put the password, it works.
If I create the same domain user ID that is in Windows AD in DB2 (VIA Control Center), I can grant permissions to it. However, I could not get the groups work (Either AD domain groups or the AD domain users added to the local linux groups).