Network Configuration with Netplan on Ubuntu 18.04

With the version 18.04 (Bionic Beaver) Ubuntu has switched to Netplan for the configuration of network interfaces.

This is a YAML based configuration system, which simplifies the configuration process. 

Configuration files

This new tool replaces the configuration file (/etc/network/interfaces) that had previously been used to configure the network interfaces on Ubuntu.
The configuration files are now located as YAML files at /etc/netplan/*.yaml. Make sure to respect the YAML standards when you edit the file as it might not work if there is a syntax error in your configuration.

A file 01-netcfg.yaml is used to configure the first interface. Below you can find the default configuration for an interface using DHCP:

# This file describes the network interfaces available on your system
# For more information, see netplan(5).
network:
  version: 2
  renderer: networkd
  ethernets:
    enp1s0f0:
      dhcp4: yes

Following you can see a list of the most common configuration options and a description of how they are used.

Configuration of a failover IP with Netplan

To configure a failover IP, you have to edit the file /etc/netplan/01-netcfg.yaml and configure a static networking for your server. The IP addresses have to be written with their CIDR notation. The netmask is /24 for the principal IP of the server and /32 for each failover IP. Your configuration file should look like in the following example:

network:
  version: 2
  renderer: networkd
  ethernets:
    enp1s0f0:
      addresses: [163.172.123.123/24, 212.83.123.123/32]
      gateway4: 163.172.123.1
      nameservers:
        addresses: [ "62.210.16.6", "62.210.16.7" ]

Once you have edited and saved the file you can reload the configuration with the following command: sudo netplan apply

Configuration of a failover IP in a virtual machine

When you configure a failover IP inside a virtual machine, you have to specify the route that will be used by the VM. Your configuration file should look like in the following example:

network:
  version: 2
  renderer: networkd
  ethernets:
    eth0:
      dhcp4: no
      dhcp6: no
      addresses: [fail.over.ip.address/32]
      gateway4: 62.210.0.1
      nameservers:
        addresses: [62.210.16.6, 62.210.16.7]
      routes:
      - to: 62.210.0.1/32
        via: fail.over.ip.address
        scope: link

source from https://www.mapachehosting.com/index.php?rp=/knowledgebase/2/Network-Configuration-with-Netplan-on-Ubuntu-18.04.html