Describe VLAN hopping.
Where an attacker crafts a package with a double 802.1Q tags. first tag is real vlan the host is on. second tag is for the "hopped-to" vlan.
This requires that the trunk uses the native VLAN.
Mitigate, mark the trunks native vlan and prune from both ends of the trunk.
- use cmd vlan dot1q tag native
- This will force the switch to tag all native vlans.