Hi At the moment, we have some Exchange 2007 servers in our main site and one CAS server. The CAS server is CAS1.mydomain.com For resilience, I would like to install another, however can't seem to find much extra information on the Internet about how to do this once the initial CAS is already up and running. There is an excellent article herehttp://www.msexchange.org/articles_tutorials/exchange-server-2007/high-availability-recovery/load-balancing-exchange-2007-client-access-servers-windows-network-technology-part1.htmlabout how to configure NLB so that two servers share the same cluster name, but does anyone know what I can do now that the first CAS is already in and being used? What would happen if I just added another CAS to the same site? Would it be used at all, or would it even break things in terms of Calendaring etc?

Hi, I don't see any functionlity will break if you introduce a new CAS. The process should be: 1. Install the CAS Role on the new server. 2. Configure all the settings same as existing CAS, that is outlook anywhere, internal and external URL properties of web directories (OWA, EWS, ActiveSync, OAB). 3. Configure NLB. Add both servers to same NLB cluster. At this time you can take a very small downtime as during the cluster formation communication between clients and CAS may be distrupted. 4. Now come the final move, change your External host name to point to NLB IP. Also, you will have to modify the autodiscover SCP to point to NLB IP. you can do this by modifying the SCP to External host name. -V