Hello dear experts!

We have system WinCC Professional V15 upd3. 2 servers (redundant) and 2 clients

Server1 is set to default Master and another Server2 is like Standby.

The distance between servers around 6 km. The tunnel is built with Ethernet + radio signal + Ethernet. Ping is around 15ms.

Client1 is located near to Master Server1 (same room) and its "Preferred server" option set to Master. Client2 is located near to Standby Server2 (same room) and its "Preferred server" option set to None.

The main problem, that Client2 always tries to get all data from Master server aka Server1, and due to the long distance between them, it leads to big issues with UI and huge lagging. Sever2 itself works good, even it also located far away from Server1, but like I understand it has project on board, and does not load pictures data like Client machine all the time.

So the main question, is it possible to force Client2 to request data from near located Server?

I mean, I cannot just check Client's property "Preferred server" = Standby server, since what will happen if near located server (Server2) will become Master server at some circumstances (eg Server1 will be down)? Then Client2 in this case still will request from server which is located somewhere else!

I put option "Preferred server" like None, but it does not help. 

Thank you in advance for any advice!