title: 404 error while trying to access Exchange 2013 ECP from one of two CAS servers
body: <p>I have been tasked with not only upgrading our environment from Exchange 2007 to Exchange 2013 but to also implement redundancy by also deploying it to our Disaster Recovery site.  To this end here is what I am trying to accomplish:</p>
  
  <p>Head Office has one CAS and one Mailbox server
  DR Site has one CAS and one Mailbox server
  I have managed to log into the CAS located at the Head Office and create a DAG, have database copies, etc.  </p>
  
  <p>Because I'm using a coexistence scenario I'm having to use <code>https://HeadOffice.mycorp.com/ecp/?ExchClientVer=15</code> and I'm able to log in and do what I need just fine.
  However, when I got to <code>https://DrSite.mycorp.com/ecp/?ExchClientVer=15</code> I get to the login page but after I log in i get a 404 Error.</p>
  
  <p>It should be noted that both sites are on different subnets.
  I have also deleting the canary data and restarted the servers as per <a href="https://social.technet.microsoft.com/Forums/exchange/en-US/777b51ee-330d-43cc-a56e-4614d44aed7b/unable-to-access-owa-or-ecp-something-went-wrong-or-500-unexpected-error?forum=exchangesvrclients" rel="nofollow">Unable to access OWA or ECP</a></p>
  
  <p>One thing I have notices and that has already tripped me up once for anyone dealing with similar issue is that you have to be careful when following advice when you have the CAS and Mailbox roles on different servers.  Alot of people and instructions assume that both are on the same machine.  Took me a while to realize that when instructions say to do something with the "Exchange Back End" that they mean, on the Mailbox server.</p>
  
  <p>I bring this up because I have also tried <a href="http://support.microsoft.com/kb/2778897" rel="nofollow">Cannot access Outlook Web App or the EAC after you re-create the "owa" or "ECP" virtual directory on an Exchange Server 2013 Mailbox server</a>
  I get the impression based on what I have read that the 404 is being returned from the Exchange Back End (aka the Mailbox server) but in my scenario how can I tell which one?</p>
  
  <p>Does anyone have any ideas of what else I can look at?</p>