Remote UI with redundant servers

[n_lev]

I'm curious about system behaviour in the following scenario.

Let's say I have a pair of redundant servers A and B. They have 1 ethernet connection between them for synchronisation. They are located in different buildings for the purposes of increased availability (in case of fire, for example)

I also have 1 client that is located in another building and have 1 ethernet card, this client talks to both servers.

Let's say server A is ACTIVE, server B is PASSIVE. In this situation any commands from the client will be processed by server A and ignored by server B.
Now, let's say there is a fault in an ethernet switch somewhere in the building of server A, as a result client looses comms to server A but still have comms to server B.
But since server A is still ATIVE and B is PASSIVE, my remote client becomes useless. Any commands it issues just get ignored since server B is PASSIVE.

How should this be handled?
The only think I came up with so far is to include Ui connection status into an error state calculation. Is that the way to do it or am I on completely a wrong track?

[leoknipp]

Hello,

your approach is the correct one. Based on the connections of your server (UI-connection, PLC-connections of the drivers, ...) and some other project specific information (user defined configuration) you have to define when a server shall increase the error-state to decide to be active or not.

Best Regards
Leopold Knipp
Senior Support Specialist

[n_lev]

Thanks Leopold