Attention has traditionally been paid to network perimeter security, such as firewall, and to mitigating Layer 3 attacks. However, networks must be protected against Layer 2 attacks, too. These are launched from devices inside the network by either a rogue device or a legitimate device that has been compromised. Rogue devices might be placed maliciously or might just be connected to an access switch by an employee wanting more switch port or wireless access. They include:
• Wireless routers or hubs
• Access switches
A switch might become the Spanning Tree root bridge and disrupt user traffic. Use root guard and bpdu guard commands to prevent this. (Spanning Tree security is discussed ...