VLAN isolation provides Layer 2 isolation between the ports in a VLAN. VLAN Isolation Application shows an application of VLAN isolation.
In this figure, ports in the Guest VLAN have access to services on the network VLAN, but Guest VLAN ports cannot access other Guest VLAN ports over Layer 2 (or the Marketing or Engineering VLANs). This provides port-to-port security at Layer 2.