High Availability

Hello!
I have a few questions on the instructions https://portal.hostingcon...high-availability.aspx

1) According to the scheme, the servers of the control panel address the mail servers. What protocols and ports?
2) What is and what is the network address of the load balancer?
3) What network address should I specify in the Host Address field? HOST IP Field.
Now in the host ip field we have local network addresses of mail servers. We want to set up high availability so that when one server fails, all requests are redirected to another. We want to properly configure our infrastructure.
If I do not change local addresses in the host ip field, how will the panel work and proxy requests?
 
Thanks