A VLAN (Virtual Local Area Network) is a logical segmentation of a physical network that allows multiple networks to exist within the same physical infrastructure. VLANs enhance network performance, security, and manageability by grouping devices logically rather than based on physical location.
Benefits of VLANs
- Improved Security – Devices in different VLANs cannot directly communicate unless explicitly configured.
- Better Network Performance – Reduces broadcast traffic and congestion.
- Simplified Management – Allows easier reconfiguration of networks without changing physical cabling.
- Enhanced Scalability – Supports large networks by dividing them into smaller segments.
How to Configure VLANs
Step 1: Define VLANs on a Switch
Access the switch using the CLI (Command Line Interface) or Web GUI.
Enter privileged EXEC mode:enable
Enter global configuration mode:configure terminal
Create a VLAN and assign it a number:
vlan 10
name Sales
exit
for additional VLANs as needed.
Step 2: Assign Ports to VLANs
Enter interface configuration mode for a specific port:
interface GigabitEthernet0/1
Assign the port to VLAN 10 (Access Mode):
switchport mode access switchport
access vlan 10
exit
Repeat for other interfaces and VLANs as needed.
Step 3: Configure Trunk Ports (for VLAN Communication Between Switches)
Enter interface configuration mode for the uplink port:
Edit interface GigabitEthernet0/24
Set the port as a trunk:
switchport mode trunk
switchport trunk allowed vlan 10,20,30
exit
Step 4: Verify VLAN Configuration
Check VLAN assignments:
show vlan brief
Check trunk status:
show interfaces trunk
Verify VLAN connectivity using ping or other network tools.
The Lazy Networker 
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