while physical separation between network segments,VLAN

rely on switching should be perfect, if not

so,misconfiguration or a bug could cause the VLAN barriers

to be broken

There i a 2 risk

1.packet leaks from one VLAN to another, possibly revealing

sensitive information

2.In the second, a specially crafted packet is injected

into another VLAN. Any attack that could cause the VLAN

barriers to break requires a machine directly attached to

the physical network. This means that only a local machine

can execute an attack against the switch.