Double Tagging adds two VLAN tags, an outer and inner tag, to traffic going to a switch as part of a Q-in-Q attack.

• A. Q-in-Q tunneling
• B. MAC Flooding
• C. Double Tagging
• D. VLAN Hopping

Answer: (C)

Double tagging is a VLAN hopping technique that uses two 802.1Q tags on a single frame. The outer tag corresponds to the VLAN on the first hop (the trunk), and the inner tag carries the destination VLAN. As the frame traverses switches on a trunk, the outer tag is stripped, leaving the inner tag to steer the frame into the target VLAN on the next switch. This allows traffic to reach a VLAN it shouldn’t normally access, bypassing some access controls on edge ports. The description’s emphasis on two tags—an outer and an inner tag—captures the exact mechanism of double tagging. Q-in-Q tunneling, while related to stacking tags for provider networks, is not inherently an attack and is distinct in its legitimate use; the two-tag approach here is the hallmark of the double tagging technique.