What attack adds two VLAN tags, known as an outer and inner tag, to the traffic going to the switch?

The correct answer is double tagging. This type of attack exploits vulnerabilities in the VLAN tagging process and is primarily associated with 802.1Q VLANs. In double tagging, an attacker sends frames that contain two VLAN tags. The outer tag is the one that the first switch reads, while the inner tag is processed by the target switch, effectively allowing the attacker to bypass VLAN segregation and potentially gain access to sensitive data that resides on another VLAN.

By including both an outer and an inner VLAN tag, the attacker is able to manipulate the network traffic in a way that it appears valid to the switch, thereby routing it to an unintended VLAN. This can lead to unauthorized access and data breaches within a network, emphasizing the need for proper VLAN configuration and security measures to prevent such incidents.

Other options such as ARP Spoofing, Dynamic ARP Inspection, and DHCP Snooping pertain to different types of network attacks or security features that are unrelated to the concept of VLAN tagging or the related vulnerabilities. Therefore, understanding the mechanics of double tagging is crucial for recognizing the risks associated with VLAN configurations in a network security context.