How can you secure VLANs in an older network environment?

1 Why VLAN security matters

VLAN security is important because VLANs share the same physical infrastructure and devices as the rest of the network, which means they are vulnerable to attacks and misconfigurations that can compromise the data and resources of the VLAN members. Some common VLAN security threats include VLAN hopping, MAC spoofing, ARP poisoning, and DHCP spoofing. These attacks can allow an attacker to bypass the VLAN boundaries and access or manipulate the traffic of other VLANs.

2 How to configure VLANs securely

One of the first steps to secure VLANs is to configure them properly on your switches and routers. You should use a consistent naming and numbering scheme for your VLANs, and avoid using the default VLAN 1, which is often used for management and control traffic. You should also assign each VLAN to a specific switch port and use port security features to limit the number of MAC addresses that can connect to each port. Additionally, you should use trunking protocols such as IEEE 802.1Q or ISL to encapsulate the VLAN traffic between switches and routers, and enable trunking security features such as native VLAN tagging, trunk allowed list, and trunk pruning.

3 How to isolate VLANs with access control lists

Another way to secure VLANs is to isolate them with access control lists (ACLs), which are rules that filter the traffic based on the source and destination IP addresses, ports, and protocols. ACLs can help you prevent unauthorized access between VLANs, as well as block unwanted traffic from external sources. You can apply ACLs on the interfaces of your routers or switches, depending on where you want to enforce the traffic filtering. You should use standard or extended ACLs, depending on the level of granularity you need, and follow the best practices of placing the most specific rules first, using implicit deny statements, and logging the denied traffic.

5 How to monitor VLANs with network tools

Monitoring VLANs is essential for maintaining their security and performance. You should use network tools such as SNMP (simple network management protocol), NMS (network management system), or IDS (intrusion detection system) to collect and analyze the VLAN traffic and activity. These tools can help you detect and troubleshoot any issues or anomalies in your VLANs, such as misconfigurations, errors, bottlenecks, or intrusions. You should also use network tools to audit and document your VLAN settings and changes, and keep them updated and consistent across your network devices.

6 How to educate VLAN users with security awareness

Finally, you should educate your VLAN users with security awareness, which is the knowledge and behavior that can help them protect the network and data from threats. You should train your VLAN users on the basic security principles and practices, such as using strong passwords, avoiding phishing emails, reporting suspicious incidents, and following the network policies and procedures. You should also communicate with your VLAN users regularly and provide them with feedback and guidance on how to improve their security posture and compliance.

7 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?