Assign private IP address prefixes to virtual machines using the Azure portal - Preview

  • Article

This article helps you add secondary IP configurations on a virtual machine NIC with a CIDR block of private IP addresses using the Azure portal. An Azure Virtual Machine (VM) has one or more network interfaces (NIC) attached to it. All the NICs have one primary IP configuration and zero or more secondary IP configurations assigned to them. The primary IP configuration has a single private IP Address assigned to it and can optionally have a public IP address assignment as well. Each secondary IP configuration can have the following items:

  • A private IP address assignment and (optionally) a public IP address assignment, OR
  • A CIDR block of private IP addresses (IP address prefix).

All the IP addresses can be statically or dynamically assigned from the available IP address ranges. For more information, see IP addresses in Azure. All IP configurations on a single NIC must be associated to the same subnet. If multiple IPs on different subnets are desired, multiple NICs on a VM can be used. For more information, see Create VM with Multiple NICs.

There's a limit to how many IP configurations can be assigned to a NIC. For more information, see the Azure limits article.

Important

The capability to add private IP address prefixes to NIC is currently in PREVIEW. See the Supplemental Terms of Use for Azure Previews for legal terms that apply to Azure features that are in beta, preview, or otherwise not yet released into general availability.

Diagram of network configuration resources created in article.

Prerequisites

  • An Azure account with an active subscription. Create an account.

  • An existing Azure virtual machine. For more information about creating a virtual machine, see Create a Windows VM or Create a Linux VM.

    • The example used in this article is named myVM. Replace this value with your virtual machine name.

  • To use this feature during Preview, you must first register. To register, complete the Onboarding Form.

Important

Before proceeding, register for this Preview by completing the Onboarding Form.

Add a dynamic private IP address prefix to a VM

You can add a dynamic private IP address prefix to an Azure network interface by completing the following steps.

  1. Sign in to the Azure portal.

  2. In the search box at the top of the portal, enter Virtual machine. Select Virtual machines in the search results.

  3. In Virtual machines, select myVM or the name of your virtual machine.

  4. Select Networking in Settings.

  5. Select the name of the network interface of the virtual machine. In this example, it's named myvm237_z1.

    Screenshot of myVM networking and network interface selection.

  6. In the network interface, select IP configurations in Settings.

  7. The existing IP configuration is displayed. This configuration is created when the virtual machine is created. To add a private and public IP address to the virtual machine, select + Add.

  8. In Add IP configuration, enter or select the following information.

    Setting Value
    Name Enter ipconfig2.
    Private IP address settings
    Private IP Address Type IP address prefix
    Allocation Select Dynamic

  9. Select OK.

    Screenshot of Add IP configuration.

    Note

    Public IP address association is not available for configuration when IP address prefix option is selected.

  10. After you change the IP address configuration, you must restart the VM for the changes to take effect in the VM.

Add a static private IP address prefix to a VM

You can add a static private IP address prefix to a virtual machine by completing the following steps.

  1. Sign in to the Azure portal.

  2. In the search box at the top of the portal, enter Virtual machine. Select Virtual machines in the search results.

  3. In Virtual machines, select myVM or the name of your virtual machine.

  4. Select Networking in Settings.

  5. Select the name of the network interface of the virtual machine. In this example, it's named myvm237_z1.

    Screenshot of myVM networking and network interface selection.

  6. In the network interface, select IP configurations in Settings.

  7. The existing IP configuration is displayed. This configuration is created when the virtual machine is created. To add a private and public IP address to the virtual machine, select + Add.

  8. In Add IP configuration, enter or select the following information.

    Setting Value
    Name Enter ipconfig2.
    Private IP address settings
    Private IP Address Type IP address prefix
    Allocation Select Static.
    IP address Enter an unused CIDR of size /28 from the subnet for your virtual machine.
    For the 10.0.0.0/14 subnet in the example, an IP would be 10.0.0.0/80.

  9. Select OK.

    Screenshot of Add static IP configuration for a private IP address block.

    Note

    When adding a static IP address, you must specify an unused, valid private IP address CIDR from the subnet the NIC is connected to.

  10. After you change the IP address configuration, you must restart the VM for the changes to take effect in the VM.

Add IP addresses to a VM operating system

Caution

This article references CentOS, a Linux distribution that is End Of Life (EOL) status. Please consider your use and planning accordingly.

Connect and sign in to a VM you created with multiple private IP addresses. You must manually add all the private IP addresses, including the primary, that you added to the VM. Complete the following steps for your VM operating system.

Windows Server

Expand

  1. Open a command prompt or PowerShell.

  2. Enter ipconfig /all at the command line. You'll see the Primary private IP address that was assigned through DHCP.

  3. Enter ncpa.cpl at the command line to open the Network Connections configuration.

  4. Open the Properties for the network adapter assigned the new IP addresses.

  5. Double-click Internet Protocol Version 4 (TCP/IPv4).

  6. Select Use the following IP address:. Enter the following values.

    Setting Value
    IP address: Enter the Primary private IP address.
    Subnet mask: Enter a subnet mask based on your IP address.
    For example, if the subnet is a /24 subnet then the subnet mask is 255.255.255.0.
    Default gateway: The first IP address in the subnet.
    If your subnet is 10.0.0.0/24, then the gateway IP address is 10.0.0.1.

  7. Select Use the following DNS server addresses:. Enter the following values.

    Setting Value
    Preferred DNS server: Enter your primary DNS server.
    Enter the IP address of 168.63.129.16 to use the default Azure provided DNS.

  8. Select the Advanced button.

  9. Select Add.

  10. Enter the private IP address you added to the Azure network interface. Enter the corresponding Subnet mask. Select Add.

  11. Repeat the previous steps to add any additional private IP addresses that you added to the Azure network interface.

Important

You should never manually assign the public IP address assigned to an Azure virtual machine within the virtual machine's operating system. When you manually set the IP address within the operating system, ensure that it's the same address as the private IP address assigned to the Azure network interface. Failure to assign the address correctly can cause loss of connectivity to the virtual machine. For more information, see Change IP address settings.

For more information about private IP addresses, see Private IP address.

  1. Select OK to close the secondary IP address settings.

  2. Select OK to close the adapter settings. Your RDP connection will re-establish.

  3. Open a command prompt or PowerShell.

  4. Enter ipconfig /all at the command line.

  5. Verify the primary and secondary private IP addresses have been added to the configuration.

    PS C:\Users\azureuser> ipconfig /all

Windows IP Configuration

   Host Name . . . . . . . . . . . . : myVM
   Primary Dns Suffix  . . . . . . . :
   Node Type . . . . . . . . . . . . : Hybrid
   IP Routing Enabled. . . . . . . . : No
   WINS Proxy Enabled. . . . . . . . : No

Ethernet adapter Ethernet:

   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : Microsoft Hyper-V Network Adapter
   Physical Address. . . . . . . . . : 00-0D-3A-E6-CE-A3
   DHCP Enabled. . . . . . . . . . . : No
   Autoconfiguration Enabled . . . . : Yes
   Link-local IPv6 Address . . . . . : fe80::a8d1:11d5:3ab2:6a51%5(Preferred)
   IPv4 Address. . . . . . . . . . . : 10.1.0.4(Preferred)
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   IPv4 Address. . . . . . . . . . . : 10.1.0.5(Preferred)
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   IPv4 Address. . . . . . . . . . . : 10.1.0.6(Preferred)
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . : 10.1.0.1
   DHCPv6 IAID . . . . . . . . . . . : 100666682
   DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-2A-A8-26-B1-00-0D-3A-E6-CE-A3
   DNS Servers . . . . . . . . . . . : 168.63.129.16
   NetBIOS over Tcpip. . . . . . . . : Enabled

  6. Ensure the primary private IP address used in windows is the same as the primary IP address of the Azure VM network interface. For more information, see No Internet access from Azure Windows VM that has multiple IP addresses.

Validation (Windows Server)

To validate connectivity to the internet from the secondary IP configuration via the public IP, use the following command. Replace 10.1.0.5 with the secondary private IP address you added to the Azure VM network interface.

ping -S 10.1.0.5 outlook.com

Note

For secondary IP configurations, you can ping to the Internet if the configuration has a public IP address associated with it. For primary IP configurations, a public IP address is not required to ping to the Internet.

SUSE Linux Enterprise and openSUSE

Expand SUSE-based distributions use the cloud-netconfig plugin from the cloud-netconfig-azure package to manage additional IP addresses. No manual configuration is required on the part of the administrator. The first IP address of an interface set on the platform is assigned via DHCP. The cloud-netconfig plugin then probes the Azure Instance Metadata Service API continuously (once per minute) for additional IP addresses assigned to the interface and adds/removes them as secondary IP addresses automatically.

This plugin should be installed and enabled on new images by default. Configuration steps for old workloads can be found here: https://www.suse.com/c/multi-nic-cloud-netconfig-ec2-azure/.

Ubuntu 14/16

Expand

We recommend looking at the latest documentation for your Linux distribution.

  1. Open a terminal window.

  2. Ensure you're the root user. If you aren't, enter the following command:

    sudo -i

  3. Update the configuration file of the network interface (assuming ‘eth0’).

    • Keep the existing line item for dhcp. The primary IP address remains configured as it was previously.

    • Add a configuration for an additional static IP address with the following commands:

      cd /etc/network/interfaces.d/
ls

      You should see a .cfg file.

  4. Open the file. You should see the following lines at the end of the file:

    auto eth0
iface eth0 inet dhcp

  5. Add the following lines after the lines that exist in the file. Replace 10.1.0.5 with your private IP address and subnet mask.

    iface eth0 inet static
address 10.1.0.5
netmask 255.255.255.0

    To add additional private IP addresses, edit the file and add the new private IP addresses on subsequent lines:

    iface eth0 inet static
address 10.1.0.5
netmask 255.255.255.0
iface eth0 inet static
address 10.1.0.6
netmask 255.255.255.0

  6. Save the file by using the following command:

    :wq

  7. Reset the network interface with the following command:

    ifdown eth0 && ifup eth0

    Important

    Execute both ifdown and ifup in the same line if using a remote connection.

  8. Verify the IP address is added to the network interface with the following command:

    ip addr list eth0

    You should see the IP address you added as part of the list. Example:

    2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
link/ether 00:0d:3a:04:45:16 brd ff:ff:ff:ff:ff:ff
inet 10.1.0.5/24 brd 10.1.0.255 scope global eth0
   valid_lft forever preferred_lft forever
inet 10.1.0.6/24 brd 10.1.0.255 scope global secondary eth0
   valid_lft forever preferred_lft forever
inet 10.1.0.4/24 brd 10.1.0.255 scope global secondary eth0
   valid_lft forever preferred_lft forever
inet6 fe80::20d:3aff:fe04:4516/64 scope link
   valid_lft forever preferred_lft forever

Validation (Ubuntu 14/16)

To ensure you're able to connect to the internet from your secondary IP configuration via the public IP associated with it, use the following command:

ping -I 10.1.0.5 outlook.com

Note

For secondary IP configurations, you can only ping to the Internet if the configuration has a public IP address associated with it. For primary IP configurations, a public IP address is not required to ping to the Internet.

For Linux VMs, when attempting to validate outbound connectivity from a secondary NIC, you may need to add appropriate routes. See appropriate documentation for your Linux distribution. The following is one method to accomplish this:

echo 150 custom >> /etc/iproute2/rt_tables 

ip rule add from 10.1.0.5 lookup custom
ip route add default via 10.1.0.1 dev eth2 table custom

  • Ensure to replace:

    • 10.1.0.5 with the private IP address that has a public IP address associated to it

    • 10.1.0.1 to your default gateway

    • eth2 to the name of your secondary NIC

Ubuntu 18.04+

Expand

Ubuntu 18.04 and above have changed to netplan for OS network management. We recommend looking at the latest documentation for your Linux distribution.

  1. Open a terminal window.

  2. Ensure you're the root user. If you are not, enter the following command:

    sudo -i

  3. Create a file for the second interface and open it in a text editor:

    vi /etc/netplan/60-static.yaml

  4. Add the following lines to the file, replacing 10.1.0.5/24 with your IP and subnet mask:

    network:
    version: 2
    ethernets:
        eth0:
            addresses:
                - 10.1.0.5/24

    To add additional private IP addresses, edit the file and add the new private IP addresses on subsequent lines:

    network:
    version: 2
    ethernets:
        eth0:
            addresses:
                - 10.1.0.5/24
                - 10.1.0.6/24

  5. Save the file by using the following command:

    :wq

  6. Test the changes with netplan try to confirm syntax:

    netplan try

    Note

    netplan try will apply the changes temporarily and roll the changes back after 120 seconds. If there is a loss of connectivity, please wait 120 seconds, and then reconnect. At that time, the changes will have been rolled back.

  7. Assuming no issues with netplan try, apply the configuration changes:

    netplan apply

  8. Verify the IP address is added to the network interface with the following command:

    ip addr list eth0

    You should see the IP address you added as part of the list. Example:

    2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
link/ether 00:0d:3a:04:45:16 brd ff:ff:ff:ff:ff:ff
inet 10.1.0.5/24 brd 10.1.0.255 scope global eth0
   valid_lft forever preferred_lft forever
inet 10.1.0.6/24 brd 10.1.0.255 scope global secondary eth0
   valid_lft forever preferred_lft forever
inet 10.1.0.4/24 brd 10.1.0.255 scope global secondary eth0
   valid_lft forever preferred_lft forever
inet6 fe80::20d:3aff:fe04:4516/64 scope link
   valid_lft forever preferred_lft forever

Validation (Ubuntu 18.04+)

To ensure you're able to connect to the internet from your secondary IP configuration via the public IP associated with it, use the following command:

ping -I 10.1.0.5 outlook.com

Note

For secondary IP configurations, you can only ping to the Internet if the configuration has a public IP address associated with it. For primary IP configurations, a public IP address isn't required to ping to the Internet.

For Linux VMs, when trying to validate outbound connectivity from a secondary NIC, you may need to add appropriate routes. There are many ways to do this. Please see appropriate documentation for your Linux distribution. The following is one method to accomplish this:

echo 150 custom >> /etc/iproute2/rt_tables 

ip rule add from 10.1.0.5 lookup custom
ip route add default via 10.1.0.1 dev eth2 table custom

  • Ensure you replace:

    • 10.1.0.5 with the private IP address that has a public IP address associated to it

    • 10.1.0.1 to your default gateway

    • eth2 to the name of your secondary NIC

Red Hat Enterprise Linux, CentOS, and others

Expand

  1. Open a terminal window.

  2. Ensure you're the root user. If you aren't, enter the following command:

    sudo -i

  3. Enter your password and follow instructions as prompted. Once you're the root user, go to the network scripts folder with the following command:

    cd /etc/sysconfig/network-scripts

  4. List the related ifcfg files using the following command:

    ls ifcfg-*

    You should see ifcfg-eth0 as one of the files.

  5. To add an IP address, create a configuration file for it as shown below. Note that one file must be created for each IP configuration.

    touch ifcfg-eth0:0

  6. Open the ifcfg-eth0:0 file with the following command:

    vi ifcfg-eth0:0

  7. Add content to the file, eth0:0 in this case, with the following command. Replace 10.1.0.5 with your additional private IP address and subnet mask.

    DEVICE=eth0:0
BOOTPROTO=static
ONBOOT=yes
IPADDR=10.1.0.5
NETMASK=255.255.255.0

  8. Save the file with the following command:

    :wq

  9. To add additional private IP addresses to the network configuration, create additional config files and add the IP information into the file.

    touch ifcfg-eth0:1

    vi ifcfg-eth0:1

    DEVICE=eth0:1
BOOTPROTO=static
ONBOOT=yes
IPADDR=10.1.0.6
NETMASK=255.255.255.0

    :wq

  10. Restart the network services and make sure the changes are successful by running the following commands:

    systemctl restart NetworkManager.service
ifconfig

    You should see the IP address or addresses you added in the list returned.

    eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
    inet 10.1.0.4  netmask 255.255.255.0  broadcast 10.1.0.255
    inet6 fe80::6245:bdff:fe7d:704a  prefixlen 64  scopeid 0x20<link>
    ether 60:45:bd:7d:70:4a  txqueuelen 1000  (Ethernet)
    RX packets 858  bytes 244215 (238.4 KiB)
    RX errors 0  dropped 0  overruns 0  frame 0
    TX packets 1021  bytes 262077 (255.9 KiB)
    TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

eth0:0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
    inet 10.1.0.5  netmask 255.255.255.0  broadcast 10.1.0.255
    ether 60:45:bd:7d:70:4a  txqueuelen 1000  (Ethernet)

eth0:1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
    inet 10.1.0.6  netmask 255.255.255.0  broadcast 10.1.0.255
    ether 60:45:bd:7d:70:4a  txqueuelen 1000  (Ethernet)

Validation (Red Hat, CentOS, and others)

To ensure you're able to connect to the internet from your secondary IP configuration via the public IP associated with it, use the following command:

ping -I 10.0.0.5 outlook.com

Note

For secondary IP configurations, you can only ping to the Internet if the configuration has a public IP address associated with it. For primary IP configurations, a public IP address is not required to ping to the Internet.

For Linux VMs, when attempting to validate outbound connectivity from a secondary NIC, you may need to add appropriate routes. Please see appropriate documentation for your Linux distribution. The following is one method to accomplish this:

echo 150 custom >> /etc/iproute2/rt_tables 

ip rule add from 10.1.0.5 lookup custom
ip route add default via 10.1.0.1 dev eth2 table custom

  • Ensure to replace:

    • 10.0.0.5 with the private IP address that has a public IP address associated to it

    • 10.0.0.1 to your default gateway

    • eth2 to the name of your secondary NIC

Debian GNU/Linux

Expand

We recommend looking at the latest documentation for your Linux distribution.

  1. Open a terminal window.

  2. Ensure you're the root user. If you aren't, enter the following command:

    sudo -i

  3. Update the configuration file of the network interface (assuming ‘eth0’).

    • Keep the existing line item for dhcp. The primary IP address remains configured as it was previously.

    • Add a configuration for an additional static IP address with the following commands:

      cd /etc/network/interfaces.d/
ls

      You should see a .cfg file.

  4. Open the file. You should see the following lines at the end of the file:

    auto eth0
iface eth0 inet dhcp

  5. Add the following lines after the lines that exist in the file. Replace 10.1.0.5 with your private IP address and subnet mask.

    iface eth0 inet static
address 10.1.0.5
netmask 255.255.255.0

    To add additional private IP addresses, edit the file and add the new private IP addresses on subsequent lines:

    iface eth0 inet static
address 10.1.0.5
netmask 255.255.255.0
iface eth0 inet static
address 10.1.0.6
netmask 255.255.255.0

  6. Save the file by using the following command:

    :wq

  7. Restart networking services for the changes to take effect. For Debian 8 and above, this can be done using below command :

    systemctl restart networking

    For prior versions of Debian, you can use below commands:

    service networking restart

  8. Verify the IP address is added to the network interface with the following command:

    ip addr list eth0

    You should see the IP address you added as part of the list. Example:

    2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
link/ether 00:0d:3a:04:45:16 brd ff:ff:ff:ff:ff:ff
inet 10.1.0.5/24 brd 10.1.0.255 scope global eth0
   valid_lft forever preferred_lft forever
inet 10.1.0.6/24 brd 10.1.0.255 scope global secondary eth0
   valid_lft forever preferred_lft forever
inet 10.1.0.4/24 brd 10.1.0.255 scope global secondary eth0
   valid_lft forever preferred_lft forever
inet6 fe80::20d:3aff:fe04:4516/64 scope link
   valid_lft forever preferred_lft forever

Validation (Debian GNU/Linux)

To ensure you're able to connect to the internet from your secondary IP configuration via the public IP associated with it, use the following command:

ping -I 10.1.0.5 outlook.com

Note

For secondary IP configurations, you can only ping to the Internet if the configuration has a public IP address associated with it. For primary IP configurations, a public IP address is not required to ping to the Internet.

For Linux VMs, when attempting to validate outbound connectivity from a secondary NIC, you may need to add appropriate routes. See appropriate documentation for your Linux distribution. The following is one method to accomplish this:

echo 150 custom >> /etc/iproute2/rt_tables 

ip rule add from 10.1.0.5 lookup custom
ip route add default via 10.1.0.1 dev eth2 table custom

  • Ensure to replace:

    • 10.1.0.5 with the private IP address that has a public IP address associated to it

    • 10.1.0.1 to your default gateway

    • eth2 to the name of your secondary NIC

Next steps