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  • Exchange and AD

    I currently have two exchange servers and two domain controllers in my domain. Both domain controllers are replicating correctly, but when I reboot the first/main domain controller I cannot authenticate users against the Exchange server. I thought that when one domain controller goes down that exchange would know to look up the user information on another one?

  • #2
    Re: Exchange and AD

    Have you checked the DNS settings on those servers?
    How is DNS implemented in your environment?

    Is it AD integrated?
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    • #3
      Re: Exchange and AD

      Exchange keeps AD info cached and will be using only one of the DC's at a time. When you reboot one of the DC's you should check to see if Exchange is currently using that DC (look on the Directory Access tab of the Exchange server propertires in ESM). You have three choices when rebooting your DC:

      1. Wait for Exchange to update it's AD info
      2. Reboot the Exchange server
      3. Manually select the Config, DC, and GC for Exchange prior to rebooting the DC

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      • #4
        Re: Exchange and AD

        Originally posted by joeqwerty View Post
        Exchange keeps AD info cached and will be using only one of the DC's at a time. When you reboot one of the DC's you should check to see if Exchange is currently using that DC (look on the Directory Access tab of the Exchange server propertires in ESM). You have three choices when rebooting your DC:

        1. Wait for Exchange to update it's AD info
        2. Reboot the Exchange server
        3. Manually select the Config, DC, and GC for Exchange prior to rebooting the DC
        I'm guessing that DSACCESS allready builded up his cashe, so the two DC's should be available. If one becomes unavailable, DSACCESS will access the other DC or next in the list.
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        • #5
          Re: Exchange and AD

          I have both domain controllers as configured as DNS servers, but I rebooted the primary dc/dns server and exchange failed. On my exchange server I have both DNS servers listed in the network settings, but I did make the second domain controller into a DNS server until after I had setup the Exchange server.

          How can I check what's in the DSACCESS cache? EMC shows both active directory servers listed as available, but only one is showing under as Global Catalog. How can I make the other domain controller available for global catalog as well?
          Last edited by will.ton; 10th March 2008, 17:57.

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          • #6
            Re: Exchange and AD

            Does the other DC have a copy of the GC (is it also a GC server)? If so, then Exchange should discover it on it's own. If not, you need to make the other DC a GC. Exchange is configured to automatically discover the DC's it needs for the Config, DC, and GC. If you need to when rebooting a DC, you can change this from the Directory Access tab of the Exchange server properties. If these are planned reboots of the DC's then manually tell Exchange to use the other DC before you reboot.

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            • #7
              Re: Exchange and AD

              Guess the other DC doesn't have a copy of the GC. I thought exchange does that automatically?

              I guess I will try to manually add it to the other DC. Thanks for all the help!

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              • #8
                Re: Exchange and AD

                Glad to help. Just to clarify: Exchange doesn't do anything with the GC other than use it for AD information. You have to make each DC (except the first DC in a domain) a GC from the Sites and Services console. Exchange will then only use one GC (I don't know what criteria it uses to select the GC). You can, as I stated in my earlier post) force Exchange to manually use one DC/GC over the other. If you do this before rebooting the other DC you should be OK.

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                • #9
                  Re: Exchange and AD

                  Making every server a GC's is a point that needs discussion, because creating more GC's tend to increase replication traffic. yet in most environments, this isn't an issue due to the build up of the active directory. In the nevironment off Will it is adviced to make both DC's GC's. WHat does Exchange need a GC for?
                  1. Recipeint Information
                  2. GAL
                  3. Group membership mail enabled groups
                  4. messaging and mail routing


                  For authentication it accesses a domain controller and not necessary the GC.
                  If automatically discovery would be disabled, it would not discover and ellect a configuration server. In this case the severs need to be manually added to the Directory Access Tab. Exchange keeps an open connection to all servers in the tab, if one connection is lost it will use the other connection.

                  If it where to lose connections to the GC's, it would not technically fail to authenticate.
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                  • #10
                    Re: Exchange and AD

                    That's a good point about the replication traffic. Not really an issue for me since this is just for my test lab Was just trying to figure out how to avoid exchange failures if a domain controller failed.

                    Maybe I should start a new topic, but I was wondering if a lot of people cluster? Seems kind of like a waste since in 2007 its active/passive. You basically have a piece of hardware sitting idle waiting for a disaster to happen.

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                    • #11
                      Re: Exchange and AD

                      Originally posted by Killerbe View Post
                      Making every server a GC's is a point that needs discussion, because creating more GC's tend to increase replication traffic. yet in most environments, this isn't an issue due to the build up of the active directory. In the nevironment off Will it is adviced to make both DC's GC's. WHat does Exchange need a GC for?
                      1. Recipeint Information
                      2. GAL
                      3. Group membership mail enabled groups
                      4. messaging and mail routing


                      For authentication it accesses a domain controller and not necessary the GC.
                      If automatically discovery would be disabled, it would not discover and ellect a configuration server. In this case the severs need to be manually added to the Directory Access Tab. Exchange keeps an open connection to all servers in the tab, if one connection is lost it will use the other connection.

                      If it where to lose connections to the GC's, it would not technically fail to authenticate.
                      Not to be argumentative, but I don't believe that this is the case as stated above. Exchange has a DSAccess cache and will not go back to the DC/GC until the info in the cache expires. I believe that's why you have problems when you reboot one of your DC's. When you reboot, Exchange is still using info from the cache and trying to connect to the DC/GC that is in it's cache. As a test, try rebooting the other DC and see if you have problems. If you don't then I think that proves my point. If you do then Killerbe is right and that means that you have some other issue. Please post your findings so I can sleep tonight. Thanks.

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                      • #12
                        Re: Exchange and AD

                        I never have any problems when I reboot the other DC because it wasn't set as a GC. I've configured both of them as GC servers and now I can reboot either one of them and exchange still runs.

                        Killerbe mentioned about the authentication on the DC, but when I rebooted the main DC/GC server it would not let me login to OWA and I could not connect to my exchange server even though the other DC was still up and running. Perhaps an error on my side.

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                        • #13
                          Re: Exchange and AD

                          So Killerbe was correct. Thanks for posting your findings and helping to clarify things for me.

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                          • #14
                            Re: Exchange and AD

                            I have two DNS servers which are also the domain controllers. Everything seems to be functioning correctly now after I configured the second DC/GC. I powered off the main DC and exchange kept on working.

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