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Exchange Server 2016 - DAG IP Address RRS feed

  • Question

  • Hi, 

    I have a question:

    My set up:

    Exchg-1.domain.local - 192.168.80.25

    Exchg-2.domain.local - 192.168.80.26

    dag.domain.local - 192.168.80.80

    I tried to set up DNS round robin to make Outlook 2010/2016/2016 working with my Exchange set up which is in DAG in High Availability mode but that did not work. Then I decided to use DAG IP address for:

    Mail.domain.com 

    autodiscover.domain.com 

    and It worked like a charm. Exactly what I wanted it to, my Outlook works in High Availability mode but I have been told that it is not supported. 

    My question to all Exchange Experts is: 

    What will happen if I keep using DAG IP address for Outlook HA? What errors I will receive? Will DAG start working slow with more load? 

    Why it is not supported by MSFT? Who else uses this kind of set up - please share the experience. 


    • Edited by Roshi Singh Tuesday, November 27, 2018 5:36 PM
    Tuesday, November 27, 2018 5:35 PM

All replies

  • Hi Roshi,

    Per my knowledge, it supports IP-Less DAG in Exchange 2016, you don't need to assign an IP to the DAG.

    Details about IP-Less DAG see:

    Exchange 2013/2016: Create IP Less DAG with SP1 – Another Step to Simplification

    Database availability groups --- Quote:

    DAGs without an administrative access point can be created only on servers running Exchange 2019, Exchange 2016, or Exchange 2013 Service Pack 1 or later, with Windows Server 2012 R2 Standard or Datacenter edition. DAGs without cluster administrative access points have the following characteristics:

    • There is no IP address assigned to the cluster/DAG, and therefore no IP Address Resource in the cluster core resource group.
    • There is no network name assigned to the cluster, and therefore no Network Name Resource in the cluster core resource group
    • The name of the cluster/DAG is not registered in DNS, and it is not resolvable on the network.
    • A cluster name object (CNO) is not created in Active Directory.
    • The cluster cannot be managed using the Failover Cluster Management tool. It must be managed using Windows PowerShell, and the PowerShell cmdlets must be run against individual cluster members.

    For your situation, you can set DNS round robin like below:

    Create the following A records:

    mail.domain.com IN A 192.168.80.25
    mail.domain.com IN A 192.168.80.26
    autodiscover.domain.com IN A 192.168.80.25
    autodiscover.domain.com IN A 192.168.80.26

    Details about set up DNS round robin in Exchange 2016 refers to:

    Exchange 2016 DNS Round Robin Load Balancing (Part 1)

    Please note: Since the website is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information. And the changes made in the above blog is not supported officially by Microsoft.


    Best Regards,
    Niko Cheng


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.


    Click here to learn more. Visit the dedicated forum to share, explore and talk to experts about Microsoft Teams.


    • Edited by Niko.Cheng Wednesday, November 28, 2018 7:16 AM
    Wednesday, November 28, 2018 7:16 AM
  • DAG only provide high availability for Exchange databases. For Client connectivity CAS is used. In Exchange 2016 mailbox role serves mailbox/Client access/Transport functionality.

    Create DNS entries like below and this should work:-

    Mail.domain.com : - 192.168.80.25

    Mail.domain.com : - 192.168.80.26

    autodiscover.domain.com: - 192.168.80.25

    autodiscover.domain.com: - 192.168.80.26

    Wednesday, November 28, 2018 9:13 AM
  • Thank you for your answer, its so nice to see a reply that explains a lot. 

    My next question is: 

    In my firewall what IP address I should put to NAT email to my email servers? 192.168.80.25 or 26? 

    In 'Change the destination to:' what IP address should I put?



    • Edited by Roshi Singh Wednesday, November 28, 2018 2:24 PM
    Wednesday, November 28, 2018 2:17 PM
  • Thank you Mr. Ashish for your answer, its so nice to see a reply that explains a lot. 

    My question is: 

    In my firewall what IP address I should put NAT email to my email servers? 192.168.80.25 or 26? 

    Wednesday, November 28, 2018 2:17 PM
  • Hi Roshi,

    You need to create two NAT rules for your Exchange 2016 servers, each server needs its own public IP. Then, create two A records in your public DNS zone which resolve to your public IPs. Details see the link I provided before -- How to set up CAS DNS Round Robin Load Balancing. 


    Best Regards,
    Niko Cheng


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.


    Click here to learn more. Visit the dedicated forum to share, explore and talk to experts about Microsoft Teams.


    • Edited by Niko.Cheng Thursday, November 29, 2018 9:21 AM
    • Proposed as answer by Niko.Cheng Monday, December 3, 2018 3:12 AM
    Thursday, November 29, 2018 9:21 AM