Configuring multiple license server hosts is optional. It provides a way to keep LSF running if a license server host goes down.
Distributing licenses over multiple server hosts provides a fallback, in case your license server daemons fail.
With this method, you run multiple license server daemons, each with its own license file. Each license file has a SERVER line keyed to the license server host it is assigned to. The cluster is partially licensed as long as any one license server daemon is running, and fully licensed when all license server daemons are running. When a license server host is unavailable, the licenses managed by that host are unavailable. You decide how many LSF licenses to put on each license server host.