First edit : nano /etc/network/interfaces

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
#allow-hotplug eno1
#iface eno1 inet dhcp
 auto eno1
 iface eno1 inet static
         address 195.154.242.173
         netmask 255.255.255.255
         gateway 195.154.242.1
 auto eno1:0
 iface eno1:0 inet static
 address 51.158.26.20
 netmask 255.255.255.255

And that’s all there is actually.

Use this as a reference.

https://documentation.online.net/en/dedicated-server/network/ip-failover/ip-failover