Friday, September 2, 2016

Exchange 2016 Removing a DAG Network

In my project of setting up a greenfield Exchange 2016 environment, our project managers kind of jumped the gun on forcing us to install Exchange before we acquired a shiny new VM infrastructure - seems like that happens quite a bit huh?

This resulted in me having to stand up Exchange on our current/old VM environment, which was painfully slow, and Exchange didn't exactly perform well. I also had to configure separate DAG networks, one for MAPI and one for Replication since the networking was rather slow; Exchange 2016 Preferred Architecture advises to use only one NIC for both types of traffic - providing you have the infrastructure for it!

When we were finally able to get the new gear with 10GB networking, we now had to migrate those Exchange servers over; the problem was the Replication LAN was non-routable and couldn't be moved to the new VM infrastructure.

So, now I had to deal with removing the Replication DAG Network, which if you've ever done this, you've probably noticed that when you remove it, it comes back automatically because the Cluster still sees it.
The MS TechNet article on removing the DAG Network says nothing of this, it just gives you the cmdlet, which doesn't work anyhow because you'll get an error saying that you need to assign the active subnets to other networks...huh?

Here's how I finally removed the Replication DAG Network, with what did and didn't work:

What Didn't Work:

In our setup, we have two NIC's; one for MAPI, one for Replication:

First, I tried to remove the network, by clicking the "Remove" link in the EAC under Servers > Database Availability Groups > DAG Network > ReplicationDagNetwork01:

This threw an error saying to use the -IgnoreNetwork cmdlet instead, which is fine but it still leaves the network there, which isn't gonna work properly later when we migrate the VM's:

Next, I tried deleting the subnet from the Replication Network, which resulted in the cluster creating another network automatically:

Great, now we have an extra DAG network, and it has reassigned the subnet and NICs and has replication enabled.

Go ahead and Remove the first Replication network (the one without the subnet) to get us back to two networks again:

What Did work:

On each DAG node, I deleted the Replication NIC, so I'm left with just the MAPI NIC:

Give it a few minutes, and Exchange will show that the Replication DAG Network is misconfigured:

**Note** In most cases "misconfigured" is bad, but in this case we want it that way, so we can remove the network.

Now, that it's misconfigured, your can remove the subnet by clicking "View Details" on the DAG Network and hitting the minus sign "-" under Subnets:

And then remove the DAG Network itself:

Now we have one DAG Network:

Now we're where we need to be with one DAG Network for both MAPI and Replication running nicely on the 10GB LAN!


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