I believe similar questions have already been answered. But my knowledge on network is sooo poor that I cannot even tell the similarity.
I work for X and we use Y's SaaS Application. The application is at a.Y.com. But we do not want users to use a.Y.com. We want them to use a.X.com all the time and make a.Y.com invisible. But my coworkers at Network team say they can only do a URL redirect because a.Y.com is not within X's network. Is it true? Wikipedia mentions something about CName. Is CName the solution if it is no true?