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Single CAS server for multiple AD sites?

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  • Single CAS server for multiple AD sites?

    Hi all!

    New member here in the process of his first transition from 2003 to 2007.

    I've been doing a lot of reading trying to get all the info I can on our proposed setup, but there's one thing I can't seem to find.

    Our proposed setup will be as follows:

    1. Primary AD site with 2 separate MB (SVR1 and SVR2) servers and an ESXi CAS/HT (OWASVR) server.
    2. Secondary AD site (different subnet) with 1 MB/HT (SVR3) and a second MB (SVR4) servers.
    3. Tertiary AD site (different subnet) with a single MB/HT (SVR5) server and a replicated ESXi CAS/HT server (for failover).
    4. Fourth AD site (again, different subnet) with a single MB/HT (SVR6) server.

    We will be using SCR to replicate SG's to the different sites. No CCR, against my recommendation.

    My question is, do I need to add a CAS role for each site or can we get away with only a single site with an active CAS role? I know each site must have an HT. In essence, I want all users to access OWA through our main AD site while keeping MB's at separate location.

    Or, do I need to add a CAS role to the servers in the remote offices?

    As of now, we have our pilot setup:

    Site 1 with SVR1 and OWASVR currently in production with 10 IT staff mailboxes currently running.

    Site 2 has a single server, SVR3 also in production with a separate 10 users on it. The issue is, while the users at site one can currently access OWA with no issues, no one at site 2 is able to gain access. Mailflow and BB are working fine at both sites.

    They are getting this error " OWA is not accessible. There is no MS Exchange CAS server that has the necessary configuration in the AD site where the mailbox is stored."

    Thanks for any help!

  • #2
    Re: Single CAS server for multiple AD sites?

    Your error message answered your question, every site with a Exchange server with mailbox server role installed needs a CAS, period.

    Have a look at the following link, should be a good read I guess: