Hello All
Hope everyone is doing good.
Beginning with Exchange 2013 SP1 Microsoft introduced the IP-less DAG as an option. In this article, we explore how to create an IP-less DAG, as well as the pros and cons of deploying one.
Why would I want to do this?
Quite simply, its easier to set up.
With an IP-less DAG, you don’t need to pre-stage a Cluster Name Object (CNO) in Active Directory. This is especially useful for organizations that have implemented the split-permission model. You also don’t need to burn an IP address for the cluster.
Limitation
there is no conversion process to take an IP-based DAG to an IP-less DAG. You will need to create a new DAG.
The challenge is 3rd party vendors. Before implementing an IP-less DAG make sure any third-party backup software can operate without an Administrative Access Point (AAP). If your Backup software vendor requires an AAP, Please find another vendor
Lab Setup
In our example lab, we will have two multi-role servers. We also have a file server that will host our File Share Witness (FSW) directory.
we will use a single network for all replication and MAPI traffic. We will leave the DAG to configure its own networking. We will have three copies of each database. Both servers hosting an active database.
Before we create the DAG we must set the appropriate permissions on the server destined to host our File Share Witness (FSW).
To configure permissions:
From the file server click Start >> Administrative Tools >> Computer Management.
Expand Local Users and Groups.
Select Groups.
Double-click the Administrators local group.
Click Add.
Type Exchange Trusted Subsystem and click Check Names.
Create a folder called "CMFSW" in any drive on your wish and make it share with read and write Permission
Deploying an IP-less DAG
Now that our file share witness is ready, let us create a DAG. In Exchange Admin Center navigate to Servers >> Database Availability Groups and select the + (New) button.
On the DAG creation page specify the following criteria.
DAG name (1) – Whatever you wish to make it
Witness server (2) –Enter the name of a non-Exchange server
Witness directory (3) – If you do not specify a directory Exchange will create a default directory in the root of C: (in our example we went with C:\Witness).
IP address (4) – For an IP-less DAG specify 255.255.255.255.
Click Save.
Adding members to the DAG
Now that the DAG is created we need to add our mailbox servers. You can see from the screenshot below that the Member Servers column is currently empty. Select the DAG and click the Manage DAG membership (Add DAG Members icon) icon.
Click the + (Add) icon.
Select the servers you wish to add to the DAG and click the Add button. Click Ok.
Click the Save button.
At this point Exchange installs the failover cluster components on each mailbox server, checks to see whether the server already belongs to a DAG and if not, adds it to the specified DAG.
Once complete click Close.
You can now see in the Member Server column our two multi-role servers are listed. We now have an IP-less DAG with two member servers and a file share witness.
Finally add the database copy for each databases on respectives servers and save
Finally use the powershell command to check the replication status : Test-ReplicationHelath
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