Question : Exchange 2010 CAS and certificates

hi,
we are upgrading from exchange 2003 to 2010, with co-existing scenario.
before installing the first CAS server (NLB), there're few things i need to confirm regarding certificates, and please correct me if i was wrong.

1. we will use mail.company.com (which is current name of exchange 2003 OWA, and will be used for new Exchange 2010 domain) and legacy.company.com

2. we have to generate CSR from the exchange (CAS) server, which means we can't get any certs before the CAS installed?

3. can we go ahead installing first exchange 2010 server (CAS+HT combined) while waiting for the certs (UCC/SAN) to be ready. will that break anything at all? I imagine that once we have CAS 2010 up, without changing anything, internal  2003 mailbox client will see no impact and OWA users can still access their 2003 mailbox via mail.company.com which then received by our reverse proxy and passed to the 2003 Front End? so again, no impact to production up to this point?

4. if we then deploy the mailbox server and create test mailbox, I imagine we can connect to this 2010 mailbox internally if we set internal DNS to point mail.company.com to the CAS server?

5. once we have SAN certificate ready, containing mail.company.com, legacy.company.com, autodiscover.company.com, we can then install it to exchange 2010 CAS. do we need to have separate certificate legacy.company.com for exchange 2003 Front End or it's already sorted by the SAN cert installed on CAS?

6. can we export this SAN cert with private key to be imported to ISA (2006) server?

Thanks for your help.

Answer : Exchange 2010 CAS and certificates

Your steps are fine. You can use the same export and use the same certificate on ISA and Exchange 2003.

There is no impact to your existing environment as long as you do not point your mail.company.com record to your Exchange 2010 CAS.

Before pointing your external mail.company.com record to Exchange 2010 CAS,  suggest test all functionalities locally...

Have a look at :
http://ilantz.wordpress.com/2010/03/12/how-to-publish-exchange-2003-and-exchange-2010-with-isa-2006/