Exchange 2013 / 2013 Coexistence - OWA rendering on 2010 CAS for 2013 Mailbox

Question

So I'm running Exchange 2013 CU2v2 alongside Exchange 2010 SP3 (both on top of 2008 R2 SP1) and I'm having a bit of a weird thing happen when migrating test users from Exchange 2010 to 2013. 
After migrating a user from a database on the 2010 server to a database on the 2013 server, when you access OWA (through a url pointing at the 2013 server), it still appears to render on the 2010 CAS (and functions normally). If you click ? > About it
shows properly that the mailbox server is the 2013 server, but the host address and client access server are still the old 2010 server. It seems that after a few hours it fixes itself. ECP, however, renders properly on the 2013 server immediately after migration.
The migration completes successfully with no errors, and outlook connects fine after migration, hitting the 2013 CAS.
I thought maybe this had to do with the Exchange Information Systems Cache, as in 2010 this was occasionally an issue:
http://www.terminal.com/blog/bid/70313/Moving-Mailboxes-During-an-Exchange-Migration
but the mailbox will still render on the 2010 CAS even after restarting the ExchangeIS service.
I should also note that this behavior DID NOT occur with Exchange 2013 CU1 alongside 2010, and only started happening after upgrading to CU2v2.
Does anyone have any thoughts as to why this is happening and what I can do to make it transition quickly to render OWA against the new mailbox? Thanks!

Answer 1

Exact same symptoms here;
Single site, 1 Exchange 2013 CU3 on 2012 Server, 1 Exchange 2010 SP3 as source for migration;
Exchange 2013 configured as external access 'cas' owa etc. and proxy to 2010.
Accessing an 2010 mailbox thu 2013 works correctly (OWA, ECP, ActiveSync, Outlook Anywhere etc.)
Created new mailbox on 2010, migrated to 2013 and this mailbox is accessed/proxied thru OWA 2010. Strangely this mailbox is hosted on the proxying 2013 server now but still gets proxied. ECP for this user does instantly connect to the correct 2013 server.
The 2010 OWA connecting to 2013 mailbox server: help | about:
Host address: https://ex2010.corp.local/owa
Version: 14.3.174.1
Proxy host address: https://ex2013/owa
Proxy version: 15.0.775.0
Proxy server name: ex2013
S/MIME control: not installed
Exchange Client Access server name: ex2010.corp.local
Exchange Client Access server .NET Framework version: 2.0.50727.5472
Client Access server version: 14.3.123.0
Client Access server platform: 64bit
Mailbox server name: ex2013.corp.local
Mailbox server Microsoft Exchange version: 15.0.775.0
Other Microsoft Exchange server roles currently installed on the Client Access server: Mailbox, Hub Transport
Authentication type associated with this Outlook Web App session: Basic
Authentication type for Exchange Client Access server to Client Access server proxy session: Negotiate
Public logon: Yes
So to me is that the 2013 server is still proxying to 2010 and the 2010 CAS is accessing the mailbox on 2013 ;).
This even when the mailbox is moved on the 2013 server itself!!
How strange is this?!
Regards,
Arian van der Pijl
Hello!