VLAN Hopping Prevention

VLAN hopping is a network attack where an attacker exploits vulnerabilities in the way VLANs are configured to gain unauthorized access to traffic on different VLANs. Here are several techniques to prevent VLAN hopping:

1. Disable Dynamic Trunking Protocol (DTP): Dynamic Trunking Protocol (DTP) is a Cisco proprietary protocol used to negotiate trunk links between switches. Disabling DTP on access ports prevents attackers from negotiating trunk connections and accessing multiple VLANs.

2. Disable Unused Ports: Disable unused switch ports to prevent attackers from plugging into these ports and gaining access to the VLANs configured on them.

3. Enable Port Security: Configure port security to limit the number of MAC addresses allowed on a switch port. This prevents attackers from connecting rogue devices to gain unauthorized access to VLANs.

4. Use VLAN Access Control Lists (VACLs): Implement VLAN Access Control Lists (VACLs) to filter traffic between VLANs at Layer 2. VACLs can be used to restrict traffic based on source and destination MAC addresses, preventing unauthorized VLAN-to-VLAN communication.

5. Implement Private VLANs (PVLANs): Private VLANs segment a VLAN into sub-VLANs, allowing finer-grained control over communication between devices within the same VLAN. PVLANs can prevent lateral movement by isolating devices from each other.

6. VLAN Pruning: Configure VLAN pruning to limit the distribution of VLAN traffic across trunk links. By pruning unnecessary VLANs from trunk links, you reduce the attack surface for VLAN hopping.

7. Enable PortFast on Access Ports: PortFast enables fast port initialization on access ports, reducing the time it takes for a port to transition to the forwarding state. This prevents attackers from exploiting spanning tree protocol (STP) convergence to gain access to VLANs.

8. Use Encrypted VLAN Trunks: Implement encrypted VLAN trunks using protocols like IEEE 802.1AE (MACsec) to secure traffic between switches and prevent eavesdropping and tampering.

9. Implement VLAN ACLs (VACLs): Configure VLAN ACLs (VACLs) to filter traffic within VLANs based on Layer 3 and Layer 4 information. VACLs can prevent unauthorized access to sensitive resources within VLANs.

10. Regular Security Audits: Conduct regular security audits and vulnerability assessments to identify and remediate any misconfigurations or vulnerabilities that could be exploited for VLAN hopping attacks.