Hi Mario,
I have a few apps that require an Active/Passive type of configuration behind the VIP. I created each node as a service with its required monitor and settings. Create a LB Vserver for the secondary node and make it non-addressable. Bind the service you configured for the Secondary node.
Create a LB Vserver for Primary node, this time with the VIP you want to use along with other settings. Bind the Primary node service you created. Under the Protection Advanced settings Add the Secondary LB Vserver you created as the "Backup Virtual Server". Save it and you should be good to go assuming both VServers are in an UP state. There are some other options within the Protection settings, but the default should accomplish what you want by having an Active/Standby service behind the VIP.
Also the Priority Load Balancing NS Feature may be another option to accomplish this, perhaps even better... I haven't used it yet so can't say one way or another.
Good luck.
