none
CAS SERVER MULTIPLE SITES RRS feed

  • Question

  • i have two sites. Each site has exc 2010 mailbox and cas server.Only one cas server is internet -facing. When a site1 user(mailbox is resides on site1) goes to site2 location and logon to this domain, his outlook connection status showing site1 cas server for directory and mail. is this normal? i would now that when a user goes toı another site that has cas server, all outlook connections goes over this site's local cas server. But in my environment according to outlook connections status, each client connecting their mailboxes which resides on different site, over remote their cas server.
    Tuesday, April 13, 2010 11:26 AM

Answers

  • I can see what your trying to achieve biblo45, by trying to have your roaming users connect locally to their closest CAS Server. There is a scenario using the CASArray option where this is possible, and I'll detail shortly.

    But, for arguments sake, lets assume this behaviour occured out of the box. If Outlook was more intelligent and dynamically connected to the local CAS Server, this CAS server would still have to talk back to the mailbox server that had your active mailbox. And even in a DAG or Standalone scenario, the active database is still across the WAN. So from a network perspective - the outlook end point might have changed - but the data has to travel the same distance.

    Which bring me onto how you could address your concern. Firstly, you need to be able to stretch a Layer 2 Subnet across sites. For Example, let s say 192.168.10.x was strettched between Site A and Site B. We can then introduce a pair of quality Hardware Load Balancers such as F5 BIG IP and configure these as a active/active pair. Each Load-Balancer servicing request from its own geographical location. The CASArray is configured to use a Virtual IP Address that is hosted by the Load-Balancers and based upon your source IP Address of the connecting client (Outlook) the load-balancers can BIAS where your requests are sent to.

    So in essence, when you're at Site A, you talk to the CASArray VIP which is provided by the Load-Balacner at Site A and it has a BIAS setting that directs you to the CAS server at Site A. And Vice Versa for Site B. This still provides your outcome, as you are infact only ever talking to your local site's CAS Server, but the request from CAS to Active MBX will remain unchanged. By stretching the Subnet and getting some quality hardware you can achive your desired outcome. This is a pattern I've used for Site resilient solutions and it can scale down, but the Load Balancers can get $$$ very quicklly. But its all going to come down to budget verses need.

    Hope that helps

    Thursday, April 15, 2010 1:28 PM
  • Hi,

    Yes, that is normal behaviour. The RPCClientAccessServer value of the Mailbox Database is only a attribute to make Outlook connect CAS to retrieve the data. It's impossible to make it dynamic.

    Generally speaking, for the remote user working, that is indeed a problem. It's same in Exchange 2007.

    Thanks

    Allen

    Friday, April 16, 2010 9:24 AM
    Moderator

All replies

  • this is normal behaviour. the Database has a CAS associated with it. This can be a CAS array or the first cas server in the site (which is the default setting. so when a client connects it is looking for the CAS server or CAS array associated with the Database.
    Mitch Roberson |MCITP:Enterprise Server Admin, Messaging 2007, 2010 |MCTS:OCS with Voice Achievement |MCT |MCSE 2000\2003 |MCSE Messaging 2000\2003
    Tuesday, April 13, 2010 1:04 PM
  • Could we configure a mapi client to look local cas server instead of cas server of mailbox? Because for a multiple site scenario and with heavy roaming profiles across sites,connection problems may occur
    Tuesday, April 13, 2010 3:11 PM
  • You need to configure the mailbox databases in each site to use the RPC endpoint (CAS server) in their site as well. Note that Outlook clients probably won't get updated/redirected when you do this.
    Active Directory, 4th Edition - www.briandesmond.com/ad4/
    Tuesday, April 13, 2010 5:28 PM
  • Each MailboxDatabase has an RpcClientAccessServer field. Outlook should be connecting to the server that is specified by the database the mailbox is in.

    Tuesday, April 13, 2010 11:27 PM
  • RpcClientAccessServer field of each databases on site1 is site1CAS. This is normal behavior.So ,a user from site1 has mailbox on site1mailbox database.

    If this user goes to the site2 location and logon here, connection goes over site2cas server.Sıte2CAS looks for user1 mailbox database and finds that this database is resides on site1,after that, gets RpcClientAccessServer field from this database and learns that connection must be redirected to site1Cas. So roaming outlook profiles will only connect their original cas server instead of location local cas server.

    This is normal behaivor?

    Wednesday, April 14, 2010 8:45 AM
  • Last I checked this is normal.


    Mitch Roberson |MCITP:Enterprise Server Admin, Messaging 2007, 2010 |MCTS:OCS with Voice Achievement |MCT |MCSE 2000\2003 |MCSE Messaging 2000\2003
    Wednesday, April 14, 2010 12:16 PM
  • Is there a method to make this dynamic,

    When a user goes to site6, he should only connect sit6casserver?

    Wednesday, April 14, 2010 1:35 PM
  • you may want to look into creating a CAS array.... I'm sort of dealing with the same thing myself....

    -Brad

    Wednesday, April 14, 2010 1:46 PM
  • but cas array is a solution for site specific.For a multi site configuration i think cas array makes no difference

    Wednesday, April 14, 2010 2:22 PM
  • I can see what your trying to achieve biblo45, by trying to have your roaming users connect locally to their closest CAS Server. There is a scenario using the CASArray option where this is possible, and I'll detail shortly.

    But, for arguments sake, lets assume this behaviour occured out of the box. If Outlook was more intelligent and dynamically connected to the local CAS Server, this CAS server would still have to talk back to the mailbox server that had your active mailbox. And even in a DAG or Standalone scenario, the active database is still across the WAN. So from a network perspective - the outlook end point might have changed - but the data has to travel the same distance.

    Which bring me onto how you could address your concern. Firstly, you need to be able to stretch a Layer 2 Subnet across sites. For Example, let s say 192.168.10.x was strettched between Site A and Site B. We can then introduce a pair of quality Hardware Load Balancers such as F5 BIG IP and configure these as a active/active pair. Each Load-Balancer servicing request from its own geographical location. The CASArray is configured to use a Virtual IP Address that is hosted by the Load-Balancers and based upon your source IP Address of the connecting client (Outlook) the load-balancers can BIAS where your requests are sent to.

    So in essence, when you're at Site A, you talk to the CASArray VIP which is provided by the Load-Balacner at Site A and it has a BIAS setting that directs you to the CAS server at Site A. And Vice Versa for Site B. This still provides your outcome, as you are infact only ever talking to your local site's CAS Server, but the request from CAS to Active MBX will remain unchanged. By stretching the Subnet and getting some quality hardware you can achive your desired outcome. This is a pattern I've used for Site resilient solutions and it can scale down, but the Load Balancers can get $$$ very quicklly. But its all going to come down to budget verses need.

    Hope that helps

    Thursday, April 15, 2010 1:28 PM
  • Hi,

    Yes, that is normal behaviour. The RPCClientAccessServer value of the Mailbox Database is only a attribute to make Outlook connect CAS to retrieve the data. It's impossible to make it dynamic.

    Generally speaking, for the remote user working, that is indeed a problem. It's same in Exchange 2007.

    Thanks

    Allen

    Friday, April 16, 2010 9:24 AM
    Moderator