This article assumes that you are familiar with the general guidelines for implementing WSUS with NLB. For more information on that review Configure WSUS for Network Load Balancing.
Consider a scenario with two WSUS Servers in NLB mode. The first server installed has been declared automatically as “master”. This can be found by using the command wsusutil listfrontendservers (see Manage WSUS 3.0 SP2 from the Command Line for more information on that). This first server fails and now there is only one server in the NLB.
The second server will automatically elect itself as master. This decision is done when the server detect’s that the master server’s heartbeat is too old. This process is transparent, which means that there is no administrative task that the WSUS administrator needs to do in order to promote or demote the server.