In Cisco Catalyst switches, each switchport can be set to different VLAN Membership modes using the "switchport mode" command. This sets the port unconditionally.
The different modes include
Tag: DTP
VLAN Hopping – Layer 2 Security exploit bypass Layer 3 security
VLAN Hopping is a Layer 2 security exploit by which a malicous user connected to a switchport on a Switch assigned to a VLAN can hop on and gain access to another VLAN which otherwise is not accessible. This security exploit allows the malicous hacker to bypass the IP Securities implemented at Layer 3.
Yersinia – Free Network Testing tool for CDP,STP,VTP,DHCP,DTP,ISL,802.1Q,802.1X
Yersinia is a free Network Penetration testing tool used to test and analyse some of the most commonly used protocols on your network. Penetration testing tools of this kind will provide deep insight on network security issues. Yersinia is a UNIX based tool that works on Linux, Solaris 8, FreeBSD.
NOTE: The tool is described as a tool to perform network tests and exercise responsible actions when performing tests which includes obtaining the permission from responsible authorities. DO NOT USE THIS TOOL FOR ANY UNAUTHROSIED HACKING PURPOSES