How to configure DHCP failover in a Linux system

How to configure DHCP failover using a Linux Debian system. We’re using two Linux servers with Debian version 9 installed. The same version of isc-dhcp-server is installed on both servers.

On the DHCP principal server, DHCP service is already installed. We have installed DHCP service for the secondary server.

For testing purposes, a client Linux Debian is used.

Primary Server: Linux Debian version 9 / stretch
DHCP Software: isc-dhcp-server
Version: 4.3.5

Secondary Server: Linux Debian version 9 / stretch
DHCP Software: isc-dhcp-server
Version: 4.3.5

Client: Linux Debian version 9 / stretch .