The attacker communicates with the switch with Dynamic Trunking Protocol (DTP) messages, trying to trick the switch into thinking it is another switch that needs to trunk. If a trunk is successfully established between the attacker’s system and the switch, the attacker can gain access to all the VLANs allowed on the trunk port. In order to succeed, this attack requires a switch port that supports trunking such as desirable or auto. The end result is that the attacker is a member of all the VLANs that are trunked on the switch and can hop on all those VLANs, sending and receiving traffic.