When configuring a trunk port on a switch for inter-VLAN routing, it is recommended to configure the native VLAN to an unused VLAN in order to improve network security. By default, the native vlan is configured to vlan 1, but in most cases, you need to manually configure this to an unused vlan.
In this article, I will show you how to configure a native vlan on a Cisco switch. Because we have already published an article on trunkport configuration on Cisco switches, we won’t go deep into what trunkport is and how it enhances inter-vlan routing. You can check out the article if you don’t know much about trunkport.
So, let’s jump right into it.
What is Native VLAN in Cisco switch?
A native VLAN is a default VLAN that a packet with no dot1q tag will be forwarded to on a trunk port. When a switch receives a packet destined for another switch, which comprises multiple VLANs, it includes a tag in the packet header that identifies the specific VLAN to which the traffic is destined.
However, if the packet has no dot1q tag, it will be forwarded to the native vlan configured on such a switch. This allows devices connected to the trunk port without VLAN tagging to communicate with the network.
It is important to note that in networks with two or more switches, the native VLAN must match on both ends of a trunk link to ensure proper communication. Mismatched native VLAN configurations can result in connectivity issues and potential security vulnerabilities within the network.
How to Configure Native VLAN on Cisco Switch
In our previous article, we covered the basics concept of trunkport and how to configure them on cisco switch. so, we will focus on configuring the native VLAN on a Cisco switch in this post.
To configure the native VLAN on a trunk port, follow these steps:
Step 1: Access the configuration mode of the switch.
SW1> enable
SW1# configure terminal
Step 2: Enter the interface configuration mode for the trunk port you want to configure.
SW1(config)# interface g0/1Step 3: Change the trunk port to the desired mode (if not already set to trunk).
SW1(config-if)# switchport mode trunkStep 4: Specify the allowed VLANs for the trunk port. This step is optional, particularly if you have already performed it before
SW1(config-if)# switchport trunk allowed vlan 10,30
Step 5: Configure the native VLAN to an unused VLAN ID (e.g., VLAN 1001). This step is important for security and helps prevent unauthorized access.
SW1(config-if)# switchport trunk native vlan 1001 Ensure that the native VLAN is consistent on both ends of the trunk link. Mismatched native VLANs can result in connectivity issues and potential security vulnerabilities.. Double-check the native VLAN configuration on both switches to ensure they match.
Additionally, when configuring the native VLAN, it is advisable to choose an unused VLAN ID to enhance network security. VLAN 1, which is the default native VLAN of a Cisco switch, is often targeted by hackers. By manually assigning a different VLAN ID, you can improve security.
What is the Command to Change Native vlan?
Once you are in the interface configuration mode, you can change the native vlan using the following command: replace <vlan_number> with the desired VLAN number you want to set as the native vlan.
SW1(config-if)# switchport trunk native <vlan_number> Conclusion
In this article, we explored the concept of the native VLAN in Cisco switches and discussed its significance in inter-VLAN routing and trunk port configurations. We have also shown how to configure a native vlan on a Cisco switch. If you have any questions, you can leave them in the comment section below. I will do my best to attend to them.
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