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A VLAN (Virtual Local Area Network) is a logical segmentation of a physical network into multiple isolated networks. It helps improve performance, security, and network management.
Why Use VLANs?
- Reduces Broadcast Traffic: Limits the number of devices receiving broadcast messages.
- Enhances Security: Devices in different VLANs cannot communicate directly unless allowed.
- Simplifies Management: Devices can be moved between VLANs without changing physical connections.
How VLANs Work
VLANs are created on managed switches, and each port is assigned to a VLAN. Devices within the same VLAN can communicate, but communication between VLANs requires a router or a Layer 3 switch.
Types of VLANs:
1. Data VLAN: Used for regular user data.
- Voice VLAN: Dedicated to VoIP phones to reduce latency.
3. Management VLAN: Used for network administration.
- Native VLAN: Handles untagged traffic on trunk links.
You Should Know:
1. Configuring VLANs on a Cisco Switch
To configure VLANs on a Cisco switch, use the following commands:
Switch> enable Switch# configure terminal Switch(config)# vlan 10 Switch(config-vlan)# name Sales Switch(config-vlan)# exit Switch(config)# interface range fastEthernet 0/1 - 10 Switch(config-if-range)# switchport mode access Switch(config-if-range)# switchport access vlan 10 Switch(config-if-range)# exit
2. Inter-VLAN Routing
To enable communication between VLANs, configure inter-VLAN routing on a Layer 3 switch or router:
Router> enable Router# configure terminal Router(config)# interface gigabitEthernet 0/0.10 Router(config-subif)# encapsulation dot1Q 10 Router(config-subif)# ip address 192.168.10.1 255.255.255.0 Router(config-subif)# exit Router(config)# interface gigabitEthernet 0/0.20 Router(config-subif)# encapsulation dot1Q 20 Router(config-subif)# ip address 192.168.20.1 255.255.255.0 Router(config-subif)# exit
3. Verifying VLAN Configuration
Use the following commands to verify VLAN configuration:
Switch# show vlan brief Switch# show interfaces trunk Switch# show running-config
4. Linux Commands for Network Management
For Linux users, VLANs can be managed using the `vconfig` or `ip` command:
<h1>Create a VLAN interface</h1> sudo ip link add link eth0 name eth0.10 type vlan id 10 <h1>Assign an IP address to the VLAN interface</h1> sudo ip addr add 192.168.10.2/24 dev eth0.10 <h1>Bring the VLAN interface up</h1> sudo ip link set dev eth0.10 up <h1>Verify VLAN configuration</h1> ip -d link show eth0.10
5. Windows PowerShell Commands for VLANs
On Windows, you can use PowerShell to manage VLANs:
<h1>Get network adapter details</h1> Get-NetAdapter <h1>Set VLAN ID for a network adapter</h1> Set-NetAdapterAdvancedProperty -Name "Ethernet" -DisplayName "VLAN ID" -DisplayValue 10
What Undercode Say:
VLANs are a powerful tool for network segmentation, offering improved security, performance, and manageability. By logically dividing a network, VLANs reduce broadcast traffic and isolate sensitive data. Proper configuration and management of VLANs are essential for maintaining a secure and efficient network infrastructure. Whether you’re working with Cisco switches, Linux systems, or Windows environments, understanding VLANs is crucial for any network engineer.
Expected Output:
- Cisco Switch VLAN Configuration: Commands to create and assign VLANs.
- Inter-VLAN Routing: Steps to enable communication between VLANs.
- Linux VLAN Management: Commands to create and manage VLANs on Linux.
- Windows VLAN Configuration: PowerShell commands for VLAN management on Windows.
For further reading, refer to:
References:
Reported By: Sameh Magdy – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
