A virtual IP address is like any other IP address except it does not have a specific host or node to resolve to. It resolves at run time to a server wherever the IP is physically bound and reachable on the network.

For client applications to access the services in an active/passive cluster in a transparent way, the virtual IP address of the cluster must be supplied to the client applications. This virtual IP address is usually referred to as the "logical host." This logical host identity is a network address (or host name) and is not tied to a single cluster server.

When there is a failover, the cluster control software will resolve the virtual IP address to the physical IP address of the current active server in the cluster. The client application is not affected in any way other than experiencing a brief outage of the services.