Bridging means linking data from one server to another server, usually on a single machine. However, you can also bridge two OPC servers over a network using a tunnelling connection:

This scenario involves setting up the DataHub instances on both machines to act as OPC clients to the respective OPC servers. The DataHub instances then interface with each other over a tunnelling connection. Configure the DataHub instance on the machine with the most uptime to be the tunnelling master and the other DataHub instance to be the tunnelling slave. We recommend that all bridges be configured on just one of the DataHub instances.