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A Virtual Adapter is a non-physical network adapter installed on Windows, aiming to provide a unique interface for this Driver, or even other protocols, regardless of which physical network is active, whether A, B, or both.

 

Installation

The simplest way to install a virtual network adapter is explained next, for Windows 10.

1.On the Start menu, select the Device Manager.

2.Select the Action - Add legacy hardware option.

3.On the Add Hardware window, select the Install the hardware that I manually select from a list (Advanced) option and click Next.

4.Select the Network Adapters option and click Next.

5.Select the Microsoft item on the Manufacturer list and select the KM-TEST Loopback adapter. Click Next on the next screens.

6.Users can also use the virtual adapter offered during the installation of Npcap library, but it is a shortcut to the KM-Test Loopback adapter. Users can select this option during the installation of Npcap library.

 

Configuration

Once the virtual adapter is defined, users must enable in the adapter the usage of the Npcap sniffer library and define a fixed IP address.

1.To do so, on Control Panel - Network and Internet - Network Connections, select the properties of the configured virtual adapter.

2.On the properties window, enable the minimum number of options to decrease the network traffic to the 61850 IEDs. The main options are Npcap Packet Driver and TCP/IPv4.

3.Select the TCP/IP properties and inform a valid and fixed IP address to access the IED network.

4.Click OK to apply these changes.

 

MTU Definition

 

The virtual interface when installed, defines by default a MTU (Maximum Transmission Unit) pratically unlimited, but the physical interfaces generally use a MTU of 1500 bytes. The PRP Service starting at version 1.0.0.2 sets dynamically the MTU to 1500, so a frame generated at the virtual adapter can be transmitted to the physical adapters normally.

 

If you´d like to check or adjust the MTU for a particular interface permanently (recommended), follow these steps:

 

To check the index and MTU of existing interfaces, open a MS-DOS command window in administrator mode and type the following command:

 

netsh interface ipv4 show interfaces

 

To change the MTU of an interface, use this command:

netsh interface ipv4 set subinterface Idx mtu=1500 store=persistent

Where Idx is the interface index as shown at the example above.

 

Linking a Virtual Adapter to this Driver

To make sure that 61850 protocol's MMS messages are routed only to the virtual adapter and not to other adapters, users must inform that configuration to this Driver.

The first way to execute this configuration is by manually informing which adapter must be used by this Driver. The second way is by informing in the ServerName/Interface List option on the PRP tab a list with names of servers that execute this Driver and their respective IP addresses.

 

Fixed Definition of a Network Adapter

1.To define a fixed network adapter, open the configuration window of this Driver and, on the Setup tab, define the Physical Layer option with the value Ethernet.

2.On the Ethernet tab, select the Interface option and, on the list of addresses, select the IP address defined for the virtual adapter. This definition is mandatory for the service to start.

3.Return to the Setup tab and configure the Physical Layer option with the value None. Click OK to save this Driver's settings.

 

Dynamic Definition of a Virtual Adapter

On the PRP tab, inform in the ServerName/Interface List option a list of server names (DNS) and IP addresses in the format ServerA:IPA;ServerB:IPB, so that the same project file containing this Driver can be used without changes in at least two servers. When this Driver starts, it retrieves the name of the local computer and checks whether this list contains an IP address that corresponds to that name. If positive, this IP address is used as the IP address of the virtual interface.