14.9.11 Packet Tracer - Layer 2 Vlan Security -

interface g0/1 switchport trunk native vlan 999 Then, ensure VLAN 999 exists but is used nowhere else. No user devices, no DHCP, no routing.

Instead of using VLAN 1 (the default native VLAN), change it to, for example, VLAN 999. 14.9.11 packet tracer - layer 2 vlan security

interface g0/1 switchport mode trunk switchport nonegotiate If a port is for a user, it should be an access port, period. Don't let devices negotiate their way into privilege. Step 3: Changing the Native VLAN (Double Tagging Defense) The Threat: In a double-tagging attack, the attacker sends a frame with two 802.1Q tags. The first tag (native VLAN) is stripped off by the first switch. The second tag (say, VLAN 10) is then visible to the next switch, potentially letting the attacker hop into a restricted VLAN. interface g0/1 switchport trunk native vlan 999 Then,