Switching to a backup vpn server, keeping the IP addresses of the clients (vpn faillover)?

Question

linux

There is an openvpn server, 10 clients with a fixed IP certificate (10 pieces). Many services communicate between clients on the internal network 10.15.0.2-11 at low speeds.
Sometimes the vpn server is completely unavailable for a number of reasons, bringing everything down.
I wanted to raise a backup server, how can I save the client's subnet if the head one disappears?
In the openvpn documentation I found Implementing a load-balancing/failover configuration , where there is a phrase:
The simplest approach to a load-balanced/failover configuration on the server is to use equivalent configuration files on each server in the cluster, except use a different virtual IP address pool for each server. For example:
server1 server 10.8.0.0 255.255.255.0
server2 server 10.8.1.0 255.255.255.0
server3 server 10.8.2.0 255.255.255.0
Can anyone clarify

1. behavior of a subnet at the moment of switching?
   
2. will the IP change, with an equal configuration
   
3. What will happen after raising the vpn on the first server, will it not come out that the clients will be divided into servers?
   

.
P.S. Dumps are not critical, the main thing is to restore the vpn network in a few minutes.

Answer 1

Don't do nonsense.
Everything has been done for a long time. Read here .
Raise the second server and just use it.