Exchange 2010 DAG Step by Step - Two Member DAG in Two AD Sites article

My Server setup details as follows.

Server Description	Server Name	IP Address	Operating System	Application
Domain Controller	dc.doitfixit.local	192.168.1.100	Windows Server 2008 R2 SP1 Standard Edition
Exchange CAS/HUB server	cas.doitfixit.local	192.168.1.101	Windows Server 2008 R2 SP1 Standard Edition	Exchange Server SP2
Exchange Mailbox Server	ex1.doitfixit.local	MAPI: 192.168.1.102 Replication: 10.1.10.10	Windows Server 2008 R2 SP1 Enterprise Edition	Exchange Server SP2
Exchange Mailbox Server	ex2.doitfixit.local	192.168.1.103 Replication: 10.1.10.11	Windows Server 2008 R2 SP1 Enterprise Edition	Exchange Server SP2

As shown in above table I am using separate network for Exchange Mailbox Replication. Also keep in mind Windows Server Enterprise Editions are required for configure DAG because it starts "Cluster Service" which required Enterprise editions of Windows servers.
Lets start the configuration.
First we have to configure the both network settings in our Exchange Mailbox servers. For more information regarding Network Configuration of configuring DAG refer this article at Technet.
See network settings of ex1.doitfixit.local exchange mailbox server below.
MAPI Network

Replication Network

Remove "Register this connection's addresses in DNS" tick.

Do the same changes to other exchange server also.


We have configured each NIC in both Exchange Mailbox servers. Now we have to bring the MAPI network to top of the Bindings order. To do this press the ALT key, and then select Advanced > Advanced Settings.

Use arrows to move the MAPI network to top of the connections.

We have DB01 Mailbox database in EX1 server and DB02 in EX2 server.

Lets start the Database Availability Group configuration
See Part II of this article from below link

To do this click "New Database Availability Group" in the Mailbox node in Organization Configuration in Exchange Management Console.
When create a DAG we should specify Witness Server which is used to establish a majority node set. Its recommended to use Hub Transport Server as a witness server. But if you decide to choose other server as a witness server you must add the "Exchange Trusted Subsystem" group to the local administrators group on that server. More witness server requirement refer this Technet article.
Specify DAG Name, Witness Server and the Witness Directory as shown in below figure.



Lets add Exchange servers to this Database Availability Group. To do this click "Manage Database Availability Group Membership...".

Add Exchange Servers.

Click Finish.


if you do not have DHCP available on your network while the member servers are being added to the DAG, you will get the warning saying that "The network name "DAG01" is not online. Please check that the IP address configuration of the Database Availability Group is correct."". So if you do not have DHCP enabled in your network, you can manually assign IPs for the DAG. To do this go to properties of the DAG01 and click "IP Addresses" and add IP addresses for the group.



If your DAG Group contains exchange servers which are in different networks (Subnets) you should add all IP addresses to this list. See the "DAG Name and IP Address Requirements" section in this TechNet article.



Now I am renaming my DAG networks as MAPI and REPLICATION for easy use. Also we can Enable/Disable Replication on each networks.



To get Database Availability Group details through Exchange Management Shell run below command.
Get-DatabaseAvailabilityGroup | FL



Lets see the status of "cluster core resources". Open "Failover Cluster Manager"



Check the status of Cluster Core Resources



Let's add database copies for each mailbox servers. Also note that all copies of a database must use the same path on each server containing a copy.



Select other Mailbox Server name and click Add.


Click Finish.


Do the same steps for all Mailbox Databases. Now you can see the copy status of Mailbox Database.



Now I am disconnect the EX2 Exchange server from the network. Now you can see DB02 database is mounted to EX1 exchange server.

 

Source : 

http://www.doitfixit.com/index.php?option=com_content&view=article&id=137:exchange-2010-database-availability-groups-dagdag-step-by-step-how-to-configure-dag-step-by-step&catid=34:exchange-2010&Itemid=53