Exchange 2003 OWA/OA/AS over NAT and Exchange 2010 CAS

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BJ Small


In trying to do a migration I discovered we are using NAT for 2003 FE Services, these include RPC/HTTP, OWA and ActiveSync. I cannot do a big bang so i need to allow for coexistence during the migration.

with the users accessing these services externally using, how can i configure the CAS to interoperate and what will this mean for redirection? how do i configure this legacy name for 2003? how do configure CAS? do i simply assign the 2010 CAS the link above? how do i get CAS to redirect for users still on 2003?

Usually I would:

1. Add a new DNS for and point to exchange FE 2003

2. Change rules to point to CAS 2010

3. With Host Hotels using ipaddress/exchange as their URL is causing some concern

any suggestions and assistance is helpful.


Sembee [MVP]

I would expect that most sites are using NAT for OWA.
It doesn't really make much difference - for co-existence you still need two URLs, two IP addresses. This would be a good opportunity to wean off using the IP address, so point the users at the legacy DNS url, rather than an IP address. That would also allow you to use a commercial SSL certificate and avoid errors - very few, if any SSL providers will issue a certificate to an IP address.


Simon Butler, Exchange MVP
Blog | Exchange Resources

BJ Small

I'm not trying to be thick but in this case i would create a new URL for the new 2010 CAS and point this URL to the old IP address above, and for the legacy name i would also create a new URL as well which would point to a new IP address.


Brian Day MCITP

Generally the legacy URL will point to the same IP you have today (the 2007 CAS) and whatever OWA URL you have today is changed to point to the IP of the 2010 CAS servers.Microsoft Premier Field Engineer, Exchange
MCSA 2000/2003, CCNA
MCITP: Enterprise Messaging Administrator 2010
Former Microsoft MVP, Exchange Server
My posts are provided "AS IS" with no guarantees, no warranties, and they confer no rights.
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