The latter really isn't possible. Unreal doesn't control when or where users connect to your network. The client controls if autoconnect is used. If no autoconnect then there is no attempt to reconnect in the first place. If autoconnect *is* used, the client will attempt to reconnect to the last server, then it's up to DNS cache. Depending on client and DNS settings, the client will try to reconnect to the same server and if it's missing , the connection will fail. Some clients like mIRC can be configured to "hunt" for a server though. All of this is out of your and Unreal's control.
Unreal can't force a user off one server and onto another. There are modules that try to emulate it like the jumpserver module, but in the end it still relies on client participation.