An attacker has penetrated a network using a technique that exploits misconfigurations to bypass access control lists segregating traffic. Which of the following measures would be MOST effective in preventing this type of network breach?
Switch off Spanning Tree Protocol across the network to simplify the topology.
Permit automatic trunk link negotiation on all switch ports to maintain VLAN communication.
Apply Voice VLAN features on all user-facing ports without other restrictive measures.
Configure switch ports to disallow automatic establishment of trunk links.