Sign in Subscribe
CCNA

How to Configure VLANs on Multiple Switches

This beginner-friendly guide walks through configuring VLANs across multiple switches, covering VLAN creation, trunk configuration, and port assignments with clear step-by-step instructions and verification commands.

Jay Whale

• 3 min read
How to Configure VLANs on Multiple Switches

Setting up VLANs across multiple switches is a fundamental skill for network engineers. While it might seem complex at first, the process follows a logical sequence that becomes second nature with practice. Let's walk through configuring VLANs on multiple switches step by step.

Understanding the Basics

Before diving into configuration, remember that VLANs create logical network segments within your physical network. When you configure VLANs on multiple switches, you're extending these logical networks across your entire infrastructure. Each VLAN needs to be created on every switch where devices in that VLAN will connect.

Planning Your VLAN Setup

Start with a simple plan. For this beginner VLAN guide, we'll configure three VLANs across two switches:

  • VLAN 10: Sales Department
  • VLAN 20: Engineering Department
  • VLAN 30: Guest Network

Both switches will need trunk links between them to carry traffic for all VLANs.

Step 1: Create VLANs on Each Switch

Connect to your first switch via console and enter global configuration mode:

Switch> enable
Switch# configure terminal
Switch(config)# vlan 10
Switch(config-vlan)# name Sales
Switch(config-vlan)# exit
Switch(config)# vlan 20
Switch(config-vlan)# name Engineering
Switch(config-vlan)# exit
Switch(config)# vlan 30
Switch(config-vlan)# name Guest
Switch(config-vlan)# exit

Repeat this exact process on your second switch. Each switch must have the same VLAN numbers and names for consistency.

Trunk links carry traffic for multiple VLANs between switches. Configure the interface connecting your switches. Note that interface names may vary depending on your switch model (e.g., GigabitEthernet, FastEthernet, or simply Ethernet):

Switch(config)# interface fastethernet 0/24
Switch(config-if)# switchport mode trunk
Switch(config-if)# switchport trunk allowed vlan 10,20,30
Switch(config-if)# exit

Configure the same trunk settings on the corresponding interface of your second switch. This creates a pathway for all VLAN traffic to flow between switches.

Step 3: Assign Access Ports

Now assign specific ports to VLANs on each switch. For example, to put port FastEthernet 0/1 into VLAN 10:

Switch(config)# interface fastethernet 0/1
Switch(config-if)# switchport mode access
Switch(config-if)# switchport access vlan 10
Switch(config-if)# exit

Repeat this process for other ports, assigning them to appropriate VLANs based on which devices will connect.

Step 4: Save Your Configuration

This is a critical step that's often overlooked. Save your running configuration to startup configuration to ensure your changes persist after a reboot:

Switch# copy running-config startup-config

Or alternatively, you can use:

Switch# write memory

Repeat this on all switches to ensure your configuration is permanently saved.

Step 5: Verify Your Configuration

Always verify your VLAN setup works correctly. Use these commands to check your switch configuration:

Switch# show vlan brief

This displays all VLANs and their assigned ports. You should see your VLANs listed with their names and associated interfaces.

Check your trunk configuration:

Switch# show interfaces trunk

This shows which interfaces are trunking and which VLANs are allowed across each trunk.

Testing Connectivity

Connect devices to ports in the same VLAN on different switches and test connectivity. Devices in VLAN 10 on Switch 1 should communicate with devices in VLAN 10 on Switch 2, but not with devices in other VLANs.

Common Troubleshooting Tips

If devices can't communicate across switches:

  • Verify VLAN numbers match on both switches
  • Check that trunk links are configured on both ends
  • Ensure the required VLANs are allowed on trunk interfaces
  • Confirm access ports are assigned to the correct VLANs
  • Verify that configuration has been saved on both switches

What's Next

Now that you understand basic VLAN configuration across multiple switches, you're ready to explore more advanced topics like VLAN Trunking Protocol (VTP) for managing VLANs centrally, and inter-VLAN routing to enable communication between different VLANs.

Tools and resources for this topic