For horizontal clustering, we have to configure at least two instances of Apache Tomcat on two different physical or virtual systems. These physical machines can be on the same physical network. It also helps in providing a high-speed bandwidth to the system.
If you want to configure clustering on different networks, then you have to open the firewall between the two networks for the AJP port and the clustering port.
Time sync between the two servers
Proper network connectivity between the two servers
Firewall ports between the two servers (if you are connecting from a different network)
1. Installation of the Tomcat instance
2. Configuration of the cluster
3. Apache HTTP web server configuration for the horizontal cluster