In modern networking, VLAN (Virtual Local Area Network) configuration is essential for segmenting networks efficiently. Whether you're preparing for the CCNA exam or working as a network engineer, mastering Cisco VLAN configuration will give you a significant advantage.

This comprehensive guide covers static and dynamic VLANs, VTP (VLAN Trunking Protocol), and step-by-step configuration commands based on Cisco IOS.

What is a VLAN?

A VLAN allows you to divide a physical network into multiple logical networks. Each VLAN behaves like a separate broadcast domain, improving network security, efficiency, and manageability.

Types of VLANs

1. Static VLANs – VLAN assignment is done manually on switch ports.

2. Dynamic VLANs – VLAN membership is assigned based on the MAC address of the device using a VMPS (VLAN Management Policy Server).

VLAN Configuration Step-by-Step

Step 1: Access the Cisco Switch

Switch> enable Switch# configure terminal

Step 2: Create VLANs

Switch(config)# vlan 10 Switch(config-vlan)# name SALES Switch(config-vlan)# exit

Step 3: Assign VLANs to Interfaces

Switch(config)# interface FastEthernet0/1 Switch(config-if)# switchport mode access Switch(config-if)# switchport access vlan 10 Switch(config-if)# exit

Step 4: Configure Trunk Ports

Switch(config)# interface FastEthernet0/24 Switch(config-if)# switchport mode trunk Switch(config-if)# switchport trunk encapsulation dot1q Switch(config-if)# exit

Step 5: Verify VLAN Configuration

Switch# show vlan brief Switch# show interfaces trunk

Cisco Dynamic VLAN Configuration

Dynamic VLANs allow for port flexibility and automation using MAC addresses.

1. Configure a VMPS server to maintain VLAN-MAC mappings.

2. Use the vmps configuration on switches to allow dynamic assignments.

Note: Dynamic VLANs are less common today due to newer technologies like 802.1X and SDN.

Best Practices for VLAN Configuration

• Use meaningful VLAN names (e.g., HR, FINANCE).

• Avoid overlapping VLAN IDs.

• Keep VLAN 1 for management; do not use it for user traffic.

• Use VTP in transparent mode unless managing VLANs centrally.

• Regularly backup your VLAN database (vlan.dat).

Common VLAN Configuration Commands