Yersinia is a layer 2 vulnerability scanner with support for the
following protocols:

Cisco Discovery Protocol (CDP)
Dynamic Host Configuration Protocol (DHCP)
Dynamic Trunking Protocol (DTP)
Hot Standby Router Protocol (HSRP)
IEEE 802.1q
Spanning Tree Protocol (STP, RSTP)
Virtual Trunking Protocol (VTP)

WWW: http://yersinia.sourceforge.net/