2 datacenters active active to use same namspace mail.domain.com. What are the caveats to this? According to the link below, regional namespaces are better. http://technet.microsoft.com/en-us/library/dd351198.aspx has anyone used namespace for active\active and had any issues with CAS redirection during site failure? Do failback URLs come into picture for active\active

I did not see much information about it, May be below thread casn help you at some extent. http://social.technet.microsoft.com/Forums/en-US/exchange2010/thread/7b860890-ba78-4361-990e-5b15806e3f51/Anil MCC 2011,ITIL V3,MCSA 2003,MCTS 2010, My Blog : http://messagingschool.wordpress.com

Here's an additional link for planning namespaces http://technet.microsoft.com/en-us/library/dd351198.aspx Jonas Andersson | Microsoft Community Contributor Award 2011 | MCITP: EMA 2007/2010 | Blog: http://www.testlabs.se/blog | Follow me on twitter: jonand82

Thanks, but it is the same link I posted above in my postv and had questions on. Not sure how this is supposed to help me.

Thanks Anil, but it does not talk about namespaces much...

That article you have mentioned give some valid points so there's no point in me cutting and pasting, I'd say you read that KB again and if you have any specific concerns then post them. Generally, it depends on your requirements and what suits your env. Sukh

here are my specific questions... I have active\active DAG spanning two ad sites. Both will have internet connectivity. According to the article under the section "single namespace with multiple sites" the note below says Microsoft does not We don't recommend deploying a topology that has a single namespace and multiple Active Directory sites. If your topology uses multiple Active Directory sites, consider using a regional namespace model. My question is can I use mail.domain.com in both sites, if so are there any issues with cas proxying\redirection during failover? Since it is same name, there is no use for failback URL - right? or From the article..... The regional namespace model is recommended for any topology that involves multiple Active Directory sites that have their own Internet connectivity. The article has Microsoft recommendations and i understand them. I am looking for what other people who have implemented Active\active DAG did. Thanks

You can have active/active but I can see it causing issues. This is probably one of the reasons why a regional one is recommened. Single Namespace on the internet>clients connect to it> Go to your load-balance if used or one or the CAS server/array in one site (lets say site A)>if user's mailbox is in Site B then it will proxy the request to Site B CAS. Extra traffice for each request that come to Site A for a user whose mailbox at Site B. Site B has internet facing CAS therefore a regional one would be better. Similar for proxying, Site B has internet facing CAS server, and you have regional namespace, if user connects to Site A URL, and their mailbox is at Site B, before connecting CAS in Site will proxy them to Site B. Then the user will connect and use Site B CAS. No extra traffic due to regional namespace and proxying. So, it would probably make sense to go for the regional namespace if there are a high number of active users at that site. Sukh

Routing traffic to a site would not be difficult if we have a global load balancer that the traffic enters into before it gets in a reverse proxy ---right?

But if you load balance the requests could be bouncing around between the 2 sites, if a request goes to Site B but the user's mailbox is at Site A it will get thown over there. Not really effective. Your setup is that you have active/active so regional would make sense. You can do it but think of the bouncing.Sukh