Hi, I have 2 Active Directory sites (Headquaters and branch office). Site HQ has subnet 172.16.100.0/24, Site BO has subnet 172.16.200.0/24. Both sites have Exchange 2010 SP1 RU5 installed with all roles-HUB, CAS, MBX. I need to deploy high availability (HA) of Exchange. I know, how to make HA of HUB or MBX roles, but how can I make HA of CAS role? I read that it is not possible do CAS array between two AD sites-is it true? If yes, so how can I design it? Just now I have primary CAS with redirecting technology. Thank you for advices!Petr Weiner

Hi Yo know what to do with the mbx & hub as you've mentioned this already. The CAS array you will have to do as mentioned above. Is there something you don't understand? Maybe read through this http://www.msexchange.org/articles_tutorials/exchange-server-2010/high-availability-recovery/load-balancing-exchange-2010-client-access-servers-using-hardware-load-balancer-solution-part1.html http://blogs.technet.com/b/ucedsg/archive/2009/12/06/how-to-setup-an-exchange-2010-cas-array-to-load-balance-mapi.aspxSukh