Hi, In Exchange 2003, we have two frontend servers and one backend server. We can use two URLs (two differnet frontend servers) to access OWA. Will it be same if I have two CAS servers and one mailbox server with exchange 2007? Thank you.

In Exchange 2007, you would have one single URL for OWA, but either implement DNS Round Robin to balance requests between the two CAS nodes, or configure NLB (Network Load Balancing), in which case you would point the URL (the domain name part of it, in fact) to the IP address of the NLB "cluster". I've not worked with Exchange 2003, so I'm wondering if using two different URLs is standard practice? Otherwise, in what other respects are you wondering if Exchange 2007 is like 2003? Just for the CAS and URLs?

Sorry that I did not state my question clearly. I mean in Exchange 2003 site A SiteB one frontend server(FE1) one frontend server(FE2) one mailbox server one mailbox server In case of disater, site A is down or FE1 is down, I can simply use https://fe2 to access mails through OWA in Exchange 2007 site A SiteB one CAS (CAS1) one CAS (CAS2) one mailbox server (MBX1) one mailbox server(MBX2) we can set MBX1 server to use CAS1; set MBX2 to use CAS2; What if CAS1 is down and we need to route users to use CAS2; we have to change it through shell on the server MBX1? right? Can both servers (MBX1 and MBX2) use the same CAS server? Thank you.

Someone can go ahead and correct me if I'm wrong, but I believe that Exchange 2007 is more demanding in this respect. Each site with a MBX server also requires at least one (working) CAS in the same site (and a HT server for that matter). So (and once again, go ahead and correct me) the CAS in another site cannot stand in as a replacement for a failed CAS in an entirely different site. If you had 1 CAS and two MBX servers in the same site, yes, in THAT case, both could use the same CAS.

Exchange proxies between sites. Therefore if you have a mailbox server in site A, and users connect to OWA in site B, then you need a CAS server in Site A to get access through OWA, so that the server in Site B connects to it. Exchange 2007 and higher makes use of AD sites and services, which Exchange 2003 didn't, so the use of "Sites" in AD is much more critical. As already stated, if the servers are in the same site, then two CAS servers can access the same MBX server. You don't "set" CAS servers to mailbox servers either. They just work. Simon.Simon Butler, Exchange MVP Blog | Exchange Resources | In the UK? Hire Me.

>Exchange 2007 and higher makes use of AD sites and services, which Exchange 2003 didn't, so the use of >"Sites" in AD is much more critical. As already stated, if the servers are in the same site, then two CAS servers >can access the same MBX server. >You don't "set" CAS servers to mailbox servers either. They just work How do they decide dfferent sites? by AD sites or physical sites? Right now, we have every location in the same default site in the AD sites. Thank you.

Active Directory sites. Exchange 2007 and higher will expose a poorly designed AD sites design. If you don't look at the design then you will find that traffic going across your WAN when you don't want it to, things not work as you expect. If you have multiple physical sites you should look at splitting it up in AD sites, with the associated subnet designation etc. Simon.Simon Butler, Exchange MVP Blog | Exchange Resources | In the UK? Hire Me.

For an additional information, if there are two different AD sites and each site faces to the Internet with the ExternalURL attribute enabled, you can use CAS Redirection. For detail article, please access the link below: http://msexchangeteam.com/archive/2007/09/04/446918.aspx Hope it helps. NovakPlease remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Thanks for your link. I checked and CAS redirection is more likely dressed to one CAS with internet facing. We have two sites and each CAS at each site is internet facing. Currently, we set MBX to use CAS server at their own site. If one CAS is down at one site, should we change MBX at this site to use CAS server at another site? or redirection will take care of this? Thank you.

You don't set mailbox servers to use a CAS server. Exchange uses AD sites and services to work out what belongs where. If you lose the CAS server in a site, then you are going to have to put another CAS server in to that AD site for Exchange to work correctly. Simon.Simon Butler, Exchange MVP Blog | Exchange Resources | In the UK? Hire Me.