Adding Multiple IP Addresses (Aliases) to a Single Network Adapter

Windows allows to assign multiple IP addresses (aliases) to a single physical network adapter. This can be useful when you want to run multiple websites with unique IP addresses on the same IIS server, if you want to bind an application to a specific IP, or if you are preparing to change IP addresses on your network. In Windows, you can add a secondary (virtual) static IP address to an existing network adapter using the GUI or the command prompt.

Assigning an Additional IP Address to a Network Adapter on Windows

The Control Panel GUI can be used to add an additional IP address to the network adapter.

1. Navigate to the Control Panel –> Network and Internet –> Network and Sharing Center -> Change adapter settings (or just run the ncpa.cpl command);
2. Open the network interface properties;
3. Select TCP/IP v4 from the list of protocols and click Properties;
4. Click the Advanced button and then click Add in the IP Addresses section;
5. Specify an additional IP address, subnet mask, and click Add;
6. Save the changes.

Run the ipconfigcommand and check that there are now two IP addresses assigned to the network interface.

To check the availability of the second IP address over the network from other computers, use the ping command.

The SkipAsSource Flag and the Primary NIC IP Address

If you assign an additional IP from the Control Panel GUI, this IP address will be used for outgoing connections. There is no such thing as a primary IP address in Windows. To prevent Windows from using a specific IP address for outbound connections, you need to enable the SkipAsSource option for it.

Use PowerShell to list the IPv4 addresses assigned to network adapters on Windows:

Get-NetIPAddress | where AddressFamily -eq IPv4| Select-Object IPAddress, InterfaceAlias, SkipAsSource

In this example, SkipAsSource is set to False for all computer IP addresses. If you want to make a particular IP address the primary source, disable the SkipAsSource option for all the other IP addresses.

Get-NetIPAddress 192.168.1.90 | Set-NetIPAddress -SkipAsSource $True

Now the specified IP will not be used by Windows as a source for outgoing connections, except the cases where it is explicitly used by a specific app. Also, if the SkipAsSource flag is enabled, the second IP address will not be registered in DNS (if dynamic registration is enabled).

How to Add a Second IP Address From CMD/PowerShell

You can enable the SkipAsSource flag when adding an additional IP address from the prompt. For example, using netsh:

Netsh int ipv4 add address name="Local Area Connection" 192.168.1.92 255.255.255.0 SkipAsSource=True

List all assigned IP addresses and their SkipAsSource values:

netsh int ipv4 show ipaddresses level=verbose

Also, you can also use PowerShell to configure a second IP for an Ethernet0 network adapter:

New-NetIPAddress –IPAddress 192.168.1.92 –PrefixLength 24 –InterfaceAlias Ethernet0 –SkipAsSource $True

To allow outgoing traffic from a specific NIC IP address, change SkipAsSource to False.

Get-NetIPAddress 192.168.1.92 | Set-NetIPAddress -SkipAsSource $False

Remove the additional IP address:

Get-NetIPAddress 192.168.1.92| Remove-NetIPAddress