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virtual-network-multiple-ip-addresses-os-config.md

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Add IP addresses to a VM operating system

Connect and login 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

  1. From a command prompt, type ipconfig /all. You only see the Primary private IP address (through DHCP).

  2. Type ncpa.cpl in the command prompt to open the Network connections window.

  3. Open the properties for the appropriate adapter: Local Area Connection.

  4. Double-click Internet Protocol version 4 (IPv4).

  5. Select Use the following IP address and enter the following values:

    • IP address: Enter the Primary private IP address

    • Subnet mask: Set based on your subnet. 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.

    • Click Use the following DNS server addresses and enter the following values:

      • Preferred DNS server: If you are not using your own DNS server, enter 168.63.129.16. If you are using your own DNS server, enter the IP address for your server.

    • Click the Advanced button and add additional IP addresses. Add each of the secondary private IP addresses listed in step 8 to the NIC with the same subnet specified for the primary IP address.

      [!WARNING] If you do not follow the steps above correctly, you may lose connectivity to your VM. Ensure the information entered for step 5 is accurate before proceeding.

    • Click OK to close out the TCP/IP settings and then OK again to close the adapter settings. Your RDP connection is re-established.

  6. From a command prompt, type ipconfig /all. All IP addresses you added are shown and DHCP is turned off.

Validation (Windows)

To ensure you are able to connect to the internet from your secondary IP configuration via the public IP associated it, once you have added it correctly using steps above, use the following command:

ping -S 10.0.0.5 hotmail.com

Note

You can only ping to the internet if the private IP address you are using above has a public IP associated with it.

Linux (Ubuntu)

  1. Open a terminal window.

  2. Make sure you are the root user. If you are not, 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 this file:

    iface eth0 inet static
address <your private IP address here>
netmask <your subnet mask>

  6. Save the file by using the following command:

    :wq

  7. Reset the network interface with the following command:

    sudo ifdown eth0 && sudo ifup eth0

    [!IMPORTANT] Run 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.

Linux (Redhat, CentOS, and others)

  1. Open a terminal window.

  2. Make sure you are the root user. If you are not, enter the following command:

    sudo -i

  3. Enter your password and follow instructions as prompted. Once you are the root user, navigate 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. Be sure to update information based on your IP address.

    DEVICE=eth0:0
BOOTPROTO=static
ONBOOT=yes
IPADDR=192.168.101.101
NETMASK=255.255.255.0

  8. Save the file with the following command:

    :wq

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

    /etc/init.d/network restart
ifconfig

    You should see the IP address you added, eth0:0, in the list returned.

Validation (Linux)

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

ping -I 10.0.0.5 hotmail.com

Note

You can only ping to the internet if the private IP address you are using above has a public IP associated with it.

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 10.0.0.5 lookup custom
ip route add default via 10.0.0.1 dev eth2 table custom
  • Be sure 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