[Building Sakai] cas authentication and sakai authentication

[wendy lee]

hi, all
We have some students who hase CAS accounts and some not. And we want them all to login in with same Url.
We config sakai to CAS authentication and found they have to login with different UI. One is /portal/xlogin, the other is CAS login page.
Can the students use the same UI and not know whether he is cas user? 
Thanks

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wendy