What You Need to Know About Software Defined Networking in Hyper-V (Part 5)

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Introduction

So far in this article series, I have spent a lot of time discussing the theory behind and the components used in software defined networks for Hyper-V. In this article, I want to shift gears a bit and show you how you can go about defining logical and virtual networks.

For the sake of demonstration, we will start out by a logical network. I am going to call this particular logical network Infrastructure, but you could really call it anything you want. In private cloud environments for example, it is common to create three logical networks – Infrastructure, Public, and Tenant. It is important to understand that each logical network typically has its own IP address pool.

Defining the Infrastructure Logical Network

Begin the process of defining the Infrastructure logical network by opening the VMM console, selecting the Fabric workspace, and selecting the Logical Networks container, which you can see in Figure A.

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Figure A: Logical networks are created in the console’s Logical Networks container.

Now, right click on the Logical Networks container and select the Create Logical Network command from the shortcut menu. When you do, Windows will launch the Create Logical Network Wizard. The Wizard’s initial screen asks you to enter a name and a description for the network that you are creating. As I said before, I am going to call this particular logical network Infrastructure, but you can use any name that you want. Regardless of your chosen naming convention, it is a good idea to enter a meaningful description. It’s easy to accumulate a fairly large collection of logical networks over time and having solid descriptions in place can help to keep you from having to deal with a mess later on.

If you look at Figure B, you can see that the wizard asks you what kind of logical network you want to create. You have three choices. You can create one connected network, a VLAN based independent network, or a private VLAN network. For our purposes, we will create one connected network. Notice in the figure however, that there is a check box that you will have to select to allow the creation of VM networks on top of the logical network. When you are done, click Next.

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Figure B: Choose the option to create One Connected Network, and allow VM networks to be created on the logical network.

When you create this type of logical network, you will have to associate one or more network sites with it. When you click the Add button, VMM will automatically define a site named Infrastructure_0. The site name is defined automatically and matches the logical network name aside from the underscore zero appended to the end of the name.

It will be up to you to choose which hosts can make use of the site that is being created. In the interest of keeping things simple, choose the All Hosts option, as shown in Figure C.

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Figure C: Associate All Hosts with the network site that you are creating.

Before you will be able to click Next, you will need to associate an IP address pool with the logical network that you are creating. To do so, click the Insert Row button and click on the IP Subnet column and then enter an IP subnet in the space provided. For the sake of demonstration, we will use 10.1.1.0/10, as shown in Figure D.

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Figure D: You will need to assign an IP address range to the logical network that you are creating.

Click Next and you will see the wizard’s Summary screen. Click Finish to create the logical network. VMM will open the Jobs window and create the logical network. When the process completes, close the Jobs window.

So far we have defined an infrastructure network, but as previously mentioned, you can create additional logical networks if you want to. One of the key rules in doing so is that logical networks cannot contain overlapping subnets.

To show you what I mean, imagine for a moment that I wanted to create a Public and a Tenant logical network. To do so, I could follow the same steps that we used to create the Infrastructure network. However, the IP subnets would have to be completely different. For instance, I might assign the Public network an IP address range of 192.168.0.1/10. Similarly, I could assign the Tenant network an address range of 172.16.0.1/12. Figure E shows what it looks like when you create multiple logical networks.

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Figure E: I have created three logical networks.

So where do virtual networks come into the picture?

With the Fabric workspace selected, select the host group that you chose when you created the logical network. For example, I used the All Hosts host group, so if you are following my example then you would select the All Hosts container.

Next, right click on one of the hosts within the host group and select the Properties command from the resulting shortcut menu. When you do, the VMM console will display the host’s properties sheet.

Now, select the properties sheet’s Hardware tab and then locate the physical network adapter that you want to bind to the logical network, as shown in Figure F.

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Figure F: Locate the adapter that you want to bind to the logical network.

If you expand this adapter, you will see a Logical Network container located beneath it. When you select the Logical Network container, your logical networks will appear in a pane to the right, as shown in Figure G.

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Figure G: The VMM console displays a list of logical networks.

Go ahead and select the logical network that you want to bind to the adapter. Keep in mind that when you connect an adapter to a logical network, you will see a warning message indicating that there must be at least one other network adapter that can facilitate communications between the host server and VMM. You can see the exact warning message, shown in Figure H.

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Figure H: VMM warns you that you will need an additional network adapter to continue to facilitate communications between the host server and VMM.

As you might recall, when we defined the logical network, we chose a host group to associate it with. However, when we selected the host group, doing so does not automatically link the host group to the logical network. It merely makes the logical network available to the hosts within the host group.

Conclusion

The process of connecting a host to a logical network is often described as a host level operation. While there is some element of truth to this statement, the operation could perhaps be better described as a NIC level operation because we aren’t just connecting individual hosts to the logical network, but also individual NICs within the host.

It is also important to realize that the computers that we are connecting to the logical network are Hyper-V host servers. We aren’t placing VMs onto the logical network. VMs use virtual networks. I will show you how to create a virtual network in Part 6.

If you would like to be notified when Brien Posey releases the next part in this article series please sign up to our VirtualizationAdmin.com Real-Time Article Update newsletter.

If you would like to read the other parts in this article series please go to:

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