10 VLAN Best Practices

A virtual LAN (VLAN) is a logical grouping of network devices that share the same broadcast domain. VLANs are used to segment a network into smaller, more manageable pieces.

There are many benefits to using VLANs, but there are also some potential drawbacks. In this article, we will discuss 10 VLAN best practices that you should consider when configuring VLANs in your network.

1. Use VLANs to segment traffic

By default, all devices in a network can communicate with each other. This can be a security risk, as malicious users could potentially gain access to sensitive data.

VLANs help to mitigate this risk by segmenting traffic so that only devices in the same VLAN can communicate with each other. This means that if a malicious user gains access to one device in a VLAN, they will not be able to access any other devices in that VLAN.

It’s important to note that VLANs do not replace traditional security measures such as firewalls. However, they can provide an extra layer of protection and should be used in conjunction with other security measures.

2. Create a separate management VLAN

When you have a management VLAN, it’s easier to secure your network because all of the devices that need to be managed are on their own VLAN. This way, you can allow only the necessary traffic between the management VLAN and other VLANs, and you can more easily monitor traffic on the management VLAN.

Additionally, if there is ever an issue with the management VLAN, it won’t affect the rest of the network because the other VLANs are isolated.

3. Assign static IP addresses for all devices on the management VLAN

If you don’t use static IP addresses, the DHCP server can assign any address to a device when it connects to the network. This makes it difficult to know which device is which, especially if you have multiple devices with the same hostname.

When you use static IP addresses, you can be sure that each device will always have the same address. This makes it much easier to manage your network, because you always know which device is which.

It’s also important to use different subnets for different VLANs. This helps to keep traffic isolated and prevents devices on one VLAN from being able to communicate with devices on another VLAN.

4. Use private IP address space for the management VLAN

The management VLAN is the VLAN where you manage and configure your devices. This VLAN should be isolated from the rest of your network for security reasons. By using private IP address space, you make it more difficult for attackers to find and connect to your management VLAN.

Additionally, you should use a separate management VLAN for each type of device on your network. For example, you should have a management VLAN for switches, a management VLAN for routers, and a management VLAN for servers. This will help keep your devices organized and make it easier to manage them.

5. Don’t use DHCP on the management VLAN

The management VLAN is used for out-of-band management of devices on the network, and it should be isolated from user traffic for security reasons. If DHCP is enabled on the management VLAN, it could allow an attacker to spoof their IP address and gain access to the network.

To avoid this, make sure that DHCP is disabled on the management VLAN and that only static IP addresses are used.

6. Secure unused ports and disable unnecessary services

If a port is left open and unused, it’s an invitation for someone to come along and plug something into it. They could be a malicious attacker looking for an easy way into your network, or they could be an employee who doesn’t know any better and plugs in their own personal device. Either way, it’s a security risk that can be easily avoided by simply disabling any ports that aren’t being used.

Similarly, if there are any services running on your VLAN that aren’t absolutely necessary, disable them. The fewer services that are running, the fewer potential attack vectors there are. And if you’re not sure whether or not a service is actually being used, err on the side of caution and disable it anyway. It’s better to be safe than sorry.

7. Implement 802.1X authentication on the management VLAN

When 802.1X is enabled, only devices that have been authenticated by the network can access the VLAN. This means that unauthorized devices will be unable to access the VLAN, and therefore will not be able to access any of the devices on the VLAN.

This is important because the management VLAN typically contains devices that are critical to the operation of the network, such as routers, switches, and servers. If an unauthorized device were to gain access to the management VLAN, it could potentially cause serious problems for the network.

Implementing 802.1X authentication on the management VLAN is a simple way to help secure the network and prevent unauthorized access.

8. Enable port security on the management VLAN

The management VLAN is where you connect devices that need to be able to manage the network. This includes things like switches, routers, and firewalls. Because these devices have such high-level access, it’s important to make sure that only authorized devices are able to connect to them.

Enabling port security on the management VLAN will help to ensure that only authorized devices are able to connect. Port security can be configured to allow only a specific MAC address to connect to each port, or it can be configured to allow only a certain number of MAC addresses.

Configuring port security is a good first step in securing your management VLAN, but it’s not the only step. You should also consider using other security measures, such as ACLs and firewalls, to further secure your management VLAN.

9. Disable CDP on the management VLAN

CDP (Cisco Discovery Protocol) is a layer 2 protocol that allows network devices to share information about their configuration and capabilities. CDP is enabled by default on all Cisco devices, and it can be used to gather a wealth of information about the network, including device IP addresses, VLAN IDs, and more.

While this information can be useful for troubleshooting and managing the network, it also presents a security risk. If an attacker were to gain access to the management VLAN, they could use CDP to gather sensitive information about the network.

To mitigate this risk, it’s recommended to disable CDP on the management VLAN. This will prevent CDP packets from being sent or received on that VLAN, and it will help to keep the management VLAN secure.

10. Configure an ACL on the management VLAN SVI

The management VLAN is typically used for administrative purposes, such as accessing devices via SSH or RDP. As a result, it’s important to restrict access to only authorized users and systems.

An ACL can help you achieve this by allowing you to specify which IP addresses and/or subnets are allowed to access the management VLAN SVI. This will prevent unauthorized access and help keep your network secure.