VLAN Hopping

In today's world, where network security is crucial, VLAN hopping is one of the most common and dangerous threats to network infrastructure. VLAN hopping is a network security vulnerability that occurs when an attacker gains unauthorized access to a network by exploiting VLAN tagging protocols.

VLANs or Virtual Local Area Networks are a type of network that allows the creation of multiple logical networks within a single physical network. Each VLAN is identified by a unique VLAN ID, which is used to tag and separate traffic from different VLANs. VLAN tagging is done at the data link layer of the OSI model and is used to allow network administrators to create separate broadcast domains within a single physical network.

VLAN hopping occurs when an attacker gains unauthorized access to a VLAN by exploiting the vulnerabilities in the VLAN tagging protocol. There are several ways that an attacker can carry out a VLAN hopping attack, including Double Tagging, Switch Spoofing, and VLAN Injection.

Double Tagging:

In this type of VLAN hopping attack, the attacker sends a frame with two VLAN tags to the switch. The first tag is the attacker's VLAN ID, and the second tag is the target VLAN ID. The switch reads the first tag and places the frame in the attacker's VLAN. However, the switch also reads the second tag and forwards the frame to the target VLAN, giving the attacker access to the target VLAN.

Switch Spoofing:

In a switch spoofing attack, the attacker sends a frame with a spoofed MAC address of the switch to the target VLAN. The target VLAN receives the frame and forwards it to the switch, which reads the MAC address and places the frame in the appropriate VLAN. However, the switch does not realize that the frame has been spoofed, and it sends the frame to the attacker's VLAN as well, giving the attacker access to the target VLAN.

VLAN Injection:

In a VLAN injection attack, the attacker sends a frame to the switch with a VLAN tag that does not exist on the network. The switch reads the VLAN tag and creates a new VLAN for the frame. The attacker can then use this VLAN to gain unauthorized access to the network.

To prevent VLAN hopping attacks, network administrators should implement VLAN security best practices. These best practices include:

1. Implementing Port Security: Port security can be used to restrict the number of MAC addresses that can be learned on a port. This prevents attackers from spoofing MAC addresses and gaining access to other VLANs.

2. VLAN Access Control Lists (ACLs): VLAN ACLs can be used to restrict traffic between VLANs, preventing attackers from moving between VLANs.

3. VLAN Trunking Protocol (VTP) Security: VTP is a protocol used to manage VLANs on a network. Implementing VTP security prevents unauthorized changes to VLAN configurations.

4. Regular Security Audits: Regular security audits can help network administrators identify vulnerabilities and implement security measures to prevent VLAN hopping attacks.

In conclusion, VLAN hopping is a serious threat to network security that can be exploited by attackers to gain unauthorized access to a network. By implementing VLAN security best practices, network administrators can prevent VLAN hopping attacks and keep their networks secure.