title: How to setup SAML to mutiple domain?
body: <p>I am learning about SAML and already read many articles and forums but I still having confusion about setup IdP.
  I am using "<code>https://simplesamlphp.org</code>/"</p>
  
  <p>For example, I have 3 websites "<code>example.com</code>", "<code>one.example.com</code>", "<code>two.example.com</code>";
  All are on three different server.
  Now, I want to setup single sign on login using SAML then on which server I need to setup IdP.
  As "<code>example.com</code>" is main domain which has all the information about user.</p>
  
  <p>As I learn, when I login to "<code>example.com</code>" then it sends request to IdP.</p>
  
  <p>But I don't get any idea where I have to set IdP and what Idp contains?. 
  Its on same server where "<code>example.com</code>" hosted OR its different server and what logic I have to write on that server?
  It's simple login function OR I need to setup "simplesaml" for this and set login logic to there.</p>
  
  <p>After setting up IdP, what I need to do on other server "<code>one.example.com</code>", "<code>two.example.com</code>"?
  Do I need to install again "simplesaml" to both server and set SP and IdP?</p>
  
  <p>In sort, which server has IdP and SP? And on which server I need to install "simplesaml"?</p>
  
  <p>Thanks in advance</p>