Tuesday, January 09, 2007 12:30 AM janiquec

Using the Microsoft Loopback Adapter with Virtual Server 2005 R2

The Virtual Server 2005 R2 network architecture was designed to allow default isolation of virtual machine network traffic from other virtual machines, the Virtual Server host, and external networks. However, using the Microsoft Loopback Adapter, you can configure virtual machines to be connected to each other, the Virtual Server host, corporate networks, or the Internet. 

Using the Microsoft Loopback Adapter

The Microsoft Loopback Adapter is a built-in, software-based network interface. When you use it, network traffic between connected virtual machines and the Virtual Server host is constrained to the internal virtual network, remaining isolated from external, physical networks.

Installing the Microsoft Loopback Adaptor

Here are the steps to install the Microsoft Loopback Adaptor on Windows Server 2003 R2:

  1. On the Virtual Server host, click Start, and then click Control Panel.
  2. In the Control Panel, click Add Hardware, then click Next.
  3. In the Is The Hardware Connected dialog box, click Yes (I have already connected the hardware), and then click Next.
  4. In the Installed hardware list, click Add a new hardware device, and then click Next.
  5. In the What Do You Want The Wizard To Do check list, click Install the hardware that I manually select from a list (Advanced), and then click Next.
  6. In the Common Hardware Types list, click Network adapters, and then click Next.
  7. In the Manufacturer list, click Microsoft.
  8. In the Network Adapter list, click Microsoft Loopback Adapter, then click Next.
  9. In the Hardware To Install dialog box, click Next.
  10. In the Completing the Add Hardware Wizard dialog box, click Finish.

You must be a member of the administrators group in order to install a new network adapter in the host operating system.

Configuring the Microsoft Loopback Adaptor

The Microsoft Loopback Adaptor must be bound to Virtual Machine Network Services to allow communications through a virtual network. Follow these steps to configure the Microsoft Loopback Adaptor bindings on the Virtual Server 2005 R2 host:

  1. On the Virtual Server 2005 R2 host, click on Start and select Control Panel.
  2. Select Network Connections, right-click the local area connection associated with the Microsoft Loopback Adapter, and then select Properties.
  3. In This connection uses the following items, ensure that the Virtual Machine Network Services check box is selected.
  4. Click Internet Protocol (TCP/IP), and then click Properties.
  5. On the General tab, click Use The Following IP Address, and then type the IP address and subnet mask, but do not enter a gateway address.
  6. Click OK, and then click Close.
Creating a Virtual Network and Connecting Virtual Machines to the Host

After the Microsoft Loopback Adapter has been installed and configured on the Virtual Server host, you can create a new virtual network and connect the virtual machines.

  1. Open the Virtual Server 2005 R2 Administration Website.
  2. In the navigation pane, under Virtual Networks, click Create.
  3. In Virtual network name, type a name for the virtual network.
  4. In Network adapter on physical computer, select the Microsoft Loopback Adapter.
  5. In Disconnected virtual network adapters, select the Connected check box for any virtual machine network adapter that you want to attach to the new virtual network.
  6. In Virtual network notes, type in a description for the new virtual network, then click OK.

You can now boot the virtual machines, configure the network address for the new local connection, and configure firewall settings to enable resource sharing, as required.

Make sure to use non-routable TCP/IP addresses when you configure the Microsoft Loopback Adaptor network address properties. The network address and network mask must match between the Virtual Server host and the virtual machines.

Enabling Virtual DHCP Server on a Virtual Network

If you intend to connect several virtual machines, you can configure the Virtual DHCP Server option on the virtual network to manage and supply network configuration options to connecting virtual machines.

  1. Open the Virtual Server 2005 R2 Administration Website.
  2. In the navigation pane, under Virtual Networks, select Configure and then click the appropriate virtual network.
  3. In Virtual Network Properties, click DHCP server.
  4. Click in the Enabled check box and configure the DHCP server options as needed
  5. Click OK.


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# re: Using the Microsoft Loopback Adapter with Virtual Server 2005 R2

Sunday, September 16, 2007 10:41 PM by Patrick

Nice post....

this part saved me: "Make sure to use non-routable TCP/IP addresses when you configure the Microsoft Loopback Adaptor network address properties. The network address and network mask must match between the Virtual Server host and the virtual machines. "

I asigned "192.168.0" for both loopback and my router. After I changed the loopback to "192.168.20" it worked like a charm. For people as I who are not network gurus, it's really easy to make this kind of mistakes..

Thanks...

# re: Using the Microsoft Loopback Adapter with Virtual Server 2005 R2

Friday, October 12, 2007 8:04 AM by Alexander Groß

Is it possible to install Virtual Server 2005 on an ISA Server 2004 (that is, ISA is the host computer for a VS 2005 guest OS) and enable network access for the VS 2005 guest OS?

I'm getting errors that the network interface could not be bound by Virtual Server because either access to the interface is denied or the network connection is set up incorrectly. There's no further information to be found in the event logs.

# re: Using the Microsoft Loopback Adapter with Virtual Server 2005 R2

Friday, October 12, 2007 1:38 PM by vs-admin

Alexander Groß - Don't know of any reason right off the top. Did you verify if Virtual Machine Network Services is checked  in the connection properties for that network interface?

# re: Using the Microsoft Loopback Adapter with Virtual Server 2005 R2

Friday, October 12, 2007 6:34 PM by Alexander Groß

I found the source of the problem - it's the account the VM is running under. I couldn't find any information about the minimum rights required for this service account, so I created a new account without assigning a Windows security group. After changing the the new account to be an administrator everything works as expected.

Do you know where I can find docs on the minimum rights required for VM user accounts?

# re: Using the Microsoft Loopback Adapter with Virtual Server 2005 R2

Saturday, October 13, 2007 5:20 AM by janiquec

Alexander - Virtual Machine Account Minimum Permissions

Virtual machine folder

 Read and Execute, List Folder Contents, Read, Write

Virtual network configuration folder

Read and Execute, List Folder Contents, Read

Book plug...This info is documented in Chapter 6 of the Microsoft Virtual Server R2 Resource Kit book. This chapter is focused on Virtual Server Security and also covers information on how to set up different management and user roles. You can get the book on Amazon and other e-retailers, if you are interested.

PS - although not a Microsoft-supported configuration, you can run ISA 2004 within a virtual machine...This should not be done for a corporate production network, but for a small or home office, it works just fine. I've had this configuration running for quite some time (> 1.5 Yrs) with 4 W2K3 VMs (ISA 2004, IIS Web Server, DC/SQL, and DC/Exchange 2003) running on W2K3 X64 and VS 2005 R2.

# re: Using the Microsoft Loopback Adapter with Virtual Server 2005 R2

Wednesday, April 30, 2008 2:34 PM by Alireza

The instruction saved me a lot of time.

Thanks a lot.

# re: Using the Microsoft Loopback Adapter with Virtual Server 2005 R2

Wednesday, July 16, 2008 10:18 AM by Moiz Tankiwala

I am not a networking guru. Here's what I did to get my guest operating system to connect to the internet. But it just won't work.

Did all the configuration as described in this post, but since some of the information is not detailed out, here's what I did.

1. I have a physical network adapter (on-board) that connect to the internet and gets the internet IP, gateway and DNS information from the ISP.

2. Set up Microsoft Loopback adapter with the Virtual Machine Network Services bound to it and gave it the IP address "192.168.10.1" and network mask "255.255.255.0". As specified, I did not give the gateway address. Nothing is mentioned about the DNS and hence I did not give any DNS IP address even though "Use the following DNS server address:" is selected.

3. Configured the Virtual Server to have a Virtual Network that uses the Host's Loop back adapter.

4. Bound the Guest OS's network adapter to the Virtual Network.

5. Started the Virtaul Maching and set the Network adapter's address as "192.168.10.2" and subnet mask as "255.255.255.0". Since nothing is mentioned about the Gateway and DNS for the Guest OS's network adapter, I left it blank.

6. I am able to ping to any IP address - host's loopbak, host's internet IP, and any public IP and I am able to ping the guest OS from the host. But I cannot access any website from the guest OS. Note: I cannot ping to any domain names. only IP addresses.

I am suspecting that name resolution from within the guest OS is not working. Can any one, specially "Patrick" who has managed to get the configuration right help me configure this correctly?

Thanks in advance,

Moiz Tankiwala

http://www.moiztankiwala.com

# re: Using the Microsoft Loopback Adapter with Virtual Server 2005 R2

Wednesday, July 16, 2008 9:17 PM by vs-admin

Hi Moiz,

Are you: 1) Simply trying to configure your guest OS to be able to connect to the Internet? 2) Trying to use Internet Connection Sharing (ICS) on the host and Network Address Translation (NAT) with a Microsoft Loopback Adapter?

If you only want to achieve #1, then you do not have to use the Microsoft Loopback Adapter. All that you have to do is create a virtual network in Virtual Server that binds to the physical adapter with the external network access, then connect your virtual machine guest OS to it.

If you are trying to achieve #2, then you must configure ICS on the Microsoft Loopback Adapter, create a virtual network that is bound to the Microsoft Loopback Adapter, and connect the virtual machines guest OS to the virtual network.  Assuming you are running on Windows Server 2003, you can configure ICS through the control panel, select Network Connections, and click on the connection that provides Internet connectivity. Then, in the Local Area Connection Status dialog box, in the General tab, click Properties, then click the Advanced tab. In ICS, select the Allow Other Network Users to Connect Through This Computer's Internet Connection check box, then click OK.

Hope that gets you started!

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