Each server has a unique identifier, the "systemid," that allows servers to group together. If a server discovers another server with the same System name in a local network, they will be merged automatically.
If System names are different, the System will be added to the Resource Tree under Other Systems.
If servers are in different subnets, it is necessary to specify the other server's IP to allow them to merge in separate networks (behind NAT or over the Internet).
When servers are merged, they constantly synchronize all data so it doesn't matter which server the client is connected to. If a video is requested from a remote server, the one the client is connected to will be proxying the video traffic. Licenses are combined as well: if 4 licenses were activated on server A and 10 licenses were activated on server B, the System will have 14 licenses total after the servers are merged.
Note: Nx Witness creates a database backup automatically before merging Systems. See "Backing up and Restoring Nx Witness Database".