DAG Cross Site\Subnet networking – Additional Configuration

When you add servers to a DAG it will create a network for every subnet\NIC that server is connected to, this is nice because as soon as you add the server it can replicate with the other nodes.
However there are some post configuration steps you need to take otherwise replication will occur over the MAPI\Client network and never use the replication network.

  1. You should NEVER have multiple gateways, if you have a private\heartbeat network that is routed you need to remove the gateway and add a static route.
    Example: You configure the gateway on the public NICsimage  
    and configure the following static routes:
    Site A  image
    Site B  image
  2. Next you will notice your “DAG Networks” may look something like thisimage
    The issue with this configuration is that there is no clearly defined replication or mapi networks, so what we need to do is collapse them into 2 dag networks.
  3. Modify the networks to include both subnets, (I named mine for easy identification.
    i.e. Combine 10.0.1.x with 10.0.2.x and 192.168.2.x and 192.168.1.x
  4. I would also recommend disabling replication on the MAPI or client network, (it will be used anyway if the replication network is not available.

You should now be replicating over the replication network, you can verify with the following:

  • Get-MailboxDatabaseCopyStatus <DatabaseName> -ConnectionStatus | fl name, outgoingconnections,incomminglogcopyingnetwork

5 thoughts on “DAG Cross Site\Subnet networking – Additional Configuration

  1. Is there any point to having a private vlan in the second site if there is only 1 exchange server there? Without a private at the second site I imagine you would need 3 seperate Networks? 2x networks at the primary site (mapi with no repl, heartbeat with repl) and 1x network at the secondary (mapi with repl)?


    • what it comes down to is segmenting your traffic, optimally you would want to segment the networks in both sites…. but if they go over the same wan link you don’t gain significantly.

      if your replication is happening over the MAPI network is does use DNS lookup and SMB as well as sharing client traffic, verses TCP sockets and IP address. so there is a perf decrease there

  2. Hi Chris. Don’t you also want the -p parameter after “route” so it’s persistent across reboots? Per the help:

    C:\Users\jzs>route /?

    Manipulates network routing tables.

    ROUTE [-f] [-p] [-4|-6] command [destination]
    [MASK netmask] [gateway] [METRIC metric] [IF interface]

    -f Clears the routing tables of all gateway entries. If this is
    used in conjunction with one of the commands, the tables are
    cleared prior to running the command.

    -p When used with the ADD command, makes a route persistent across
    boots of the system. By default, routes are not preserved
    when the system is restarted. Ignored for all other commands,
    which always affect the appropriate persistent routes. This
    option is not supported in Windows 95.

  3. Thanks for sharing it, its very nice article.

    I had the same configuration, we have 4 sites each site have dedicated NIC for Replication and MAPI. Here my issue is log shipping happening through MAPI network.

    I am planning to reconfigure the DAG network as per your recommendation, so do we need to configure using set-databaseavailabilitynetwork command or is there any other way to configure.

    Please help me.

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