Ubuntu Network

ifconfig -a
ifup ensXXX
ifdown ensXXX

Primary Network Interface:

/etc/network/interfaces

Additional Network Interfaces:

/etc/network/interfaces.d/ensXXX.cfg

auto ensXXX
    iface ensXXX inet static
        address 10.100.20.10
        netmask 255.255.255.0
        hwaddress XX:XX:XX:XX:XX:XX