Exchange 2003 to 2010 upgrade networking question

Posted on 2011-03-04
Last Modified: 2012-05-11
As I understand it, the CAS handles all new traffic for web access during install (OWA, ActiveSync, Outlook Anywhere, etc.).  That being said, I have a network that essentially has a VIP that load balances 2 Exchange 2003 OWA servers that then enter our SPAM filter then onto the Exchange 2003 MBXs.

So if I change the VIP to redirect to the new CAS after install, the old 2003 environment is still active since no mailboxes have been moved, correct?  Essentially the CAS takes the traffic from the VIP, and if the mailbox exists on the 03 servers, it does a URL redirect to "", right? We have a very large environment and I really need to understand exactly how the routing works before we attempt approval.  I need to be the subject matter expert in a matter of a few weeks.

I hope I explained how it works currently.  I appreciate the assist in advance.

Question by:liquid101
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Expert Comment

ID: 35041370
u need to do the following(lets assume your current OWA(2003) URL is "")
1) Create a new Public DNS entry like "" and make it point to where "" is pointing to.

2)Now point "" to your 2010 CAS server

3)Run a command Set-OWAVirtualDirectory -Identity "CAS2010\Owa(Default WEB Site)"  -Exchage2003URL ""

4) Go have a nap or chill out as your work is done

Note:-IF you point  your VIP to point to CAS(or CAS array) , how will you load balance the Exchange 2003 ? so dont do any of those just follow the above steps

Author Comment

ID: 35043280
So what about the CAS array?  We do want to Load Balance those as well.  Which is another question.  We don't want to use Windows Load Balancer to create the array.  Does the CAS array tool allow for that or do we just need to Load Balance 2 or more CAS boxes and not worry about the array settings?

Accepted Solution

praveenkumare_sp earned 250 total points
ID: 35044793
use a hardware load balancer for your cas array(remember to Select a Load balancer that can load balance RPC requests)

Point the "" URL to hit your 2010 cas array (VIP of your cas array)

Found a awesome Website which describes the step by step approach to Create a cas array

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Author Comment

ID: 35056326
My concern is the routing, which I understand a bit better thanks to the link above (THANKS!).  In the current environment, the two OWA boxes are outside of the firewall, which then access the mailboxes inside the firewall.  With the CAS array being behind the firewall, will the URL redirect to the legacy 2003 boxes during the coexistence cause an issue?

Expert Comment

ID: 35061460
No the redirect will work just fine ;P

but understand putting the CAS before the Firewall is not a very good option, do reconsider this architecture

Author Comment

ID: 35061535
When I say behind the firewall, the CAS will be well within the confines of protected space along with the Mailbox servers.  In the older environment, however, the OWA boxes were in the DMZ as front-end servers used for authentication.

Expert Comment

ID: 35061648
I know but still

what i meant is the below
CAS->Firewall->MBX is not correct

meaning there must be no F/W between Cas and Mbx

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