A network vulnerability scanner is part of which critical element of network and system security？（）

The Cisco IOS SLB feature is a Cisco IOS-based solution that provides server load balancing.
This feature allows you to define a virtual server that represents a cluster of real servers， known asa server farm. 
When a client initiates a connection to the virtual server， the IOS SLB load balances theconnection to a chosen real server， depending on the configured load balance algorithm orpredictor. 
Which three implementation modes may be used to deploy SLB？ （）