Ignition Siemens driver doesn’t support redundancy.
In order to achieve what you want, you must use third-party tools.
For example this last post: http://forum.inductiveautomation.com/t/redundant-gw-and-redundant-plc-with-kepserver-failover-opc/9628/7
is talking about Kepware’s OPC Server Media level redundancy.
https://www.kepware.com/en-us/products/kepserverex/features/media-level-redundancy/