How to Install Gitlab on centOS 6

I have installed gitlab on centOs 6 via ssh (WHM),it’s root (WHM) for all account like http://domain1.com,http://domain2.com,http://domain3.com…,So External url for Gitlab http://domain3.com, I try to call url http://domain3.com.It’s worked,but i try to call http://domain1.com Or http://domain2.com .It’s automatically redirect to http://domain3.com.Why re-direct ? and How to resolve it ?