~$ curl icanhazip.com

# Initial configuration after ordering VPS
source /etc/network/interfaces.d/*

auto lo
iface lo inet loopback

allow-hotplug ens3
iface ens3 inet static
    address 194.67.205.100
    netmask 255.255.252.0
    gateway 194.67.204.1

# Next lines were added by me
auto ens3:1
iface ens3:1 inet static
    address 185.125.216.101
    netmask 255.255.252.0

auto ens3:2
iface ens3:2 inet static
    address 185.125.216.102
    netmask 255.255.252.0

auto ens3:3
iface ens3:3 inet static
    address 185.125.216.103
    netmask 255.255.252.0

ip netns add ns1
ip netns add ns2
and so on

# ip link set ens3:1 netns ns1