Before you can assign a user or group account an RBAC role, you must add the account to XenServer through RBAC. This requires two tasks:
After adding the user's Active Directory account or group to XenServer, in both the free XenServer product and in XenServer Advanced, the user is automatically assigned a fixed role of Pool Admin. In XenServer Enterprise and higher, you must assign a role to the user or group manually.
To change domains, leave the current domain and then join the new domain.