How do you test and validate your VLAN security posture and resilience?

1 VLAN Security Basics

Before you start testing your VLANs, you need to understand some basic principles of VLAN security. VLANs are logical groups of devices that share the same broadcast domain and can communicate without routing. VLANs are usually assigned to switch ports or interfaces using tags or identifiers. VLANs can be static or dynamic, depending on how you configure them. VLAN security involves preventing unauthorized access, spoofing, hopping, and other attacks that can exploit VLAN weaknesses.

2 VLAN Security Best Practices

To improve your VLAN security posture and resilience, you should follow best practices that reduce the attack surface and mitigate the impact of potential breaches. This includes using separate VLANs for different types of traffic, such as data, voice, and management, as well as a dedicated VLAN for untrusted devices or ports. You should also use a secure protocol, such as 802.1X, for port authentication and authorization, as well as a trunking protocol, such as 802.1Q, for VLAN tagging and encapsulation. Furthermore, you can use a firewall or access control list (ACL) to filter traffic between VLANs and enforce security policies, while VLAN access maps (VACLs) can be used to apply additional security rules within a VLAN. Lastly, private VLANs (PVLANs) are useful for isolating devices within a VLAN and preventing communication between them.

3 VLAN Security Testing Tools

Testing and validating your VLAN security posture and resilience requires the use of certain tools, such as Nmap for network discovery and security auditing, Wireshark for capturing and inspecting network traffic, Scapy for packet crafting and manipulation, Yersinia for exploiting vulnerabilities in VLAN protocols, and DTPScan for detecting and exploiting the Dynamic Trunking Protocol (DTP). All of these tools can help you scan, monitor, and analyze your network and VLANs.

4 VLAN Security Testing Methods

To test and validate your VLAN security posture and resilience, you need to apply methods that simulate different scenarios and attacks that can affect your network and VLANs. Port scanning with Nmap or other tools can help identify potential vulnerabilities and misconfigurations. Packet sniffing with Wireshark or other tools can capture and analyze your network traffic, while packet spoofing with Scapy or other tools can create and send fake packets with modified headers to bypass security controls. Additionally, VLAN hopping with Yersinia, DTPScan, or other tools can exploit the trunking or tagging mechanisms of VLANs to jump from one VLAN to another and access unauthorized resources or data in your network.

5 VLAN Security Validation Steps

To ensure the security and resilience of your VLANs, you need to plan, execute, and report your testing activities. This includes defining your testing objectives, scope, and criteria, obtaining the necessary permissions and approvals from stakeholders, selecting and configuring the appropriate tools and parameters for your testing, performing the tests in a controlled environment, documenting and analyzing the results, and reporting and communicating your findings. Additionally, you should provide recommendations on what patches or changes need to be applied to your network and VLANs to improve security.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?