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Virtual LANs (VLANs) are a fundamental networking concept that allows you to segment a physical network into multiple logical networks. This enhances security, reduces broadcast traffic, and improves performance. Below is a detailed guide on VLAN configuration, including practical commands and steps.
You Should Know:
1. VLAN Creation
To create a VLAN on a Cisco switch, use the following commands:
Switch> enable Switch configure terminal Switch(config) vlan 20 Switch(config-vlan) name IT_Department Switch(config-vlan) exit
2. Assigning Ports to VLANs
After creating a VLAN, assign switch ports to it:
Switch(config) interface gigabitEthernet 0/1 Switch(config-if) switchport mode access Switch(config-if) switchport access vlan 20 Switch(config-if) exit
3. Verifying VLAN Configuration
Check VLAN assignments with:
Switch show vlan brief
To see which ports belong to a VLAN:
Switch show interfaces trunk
4. Trunk Port Configuration (Inter-Switch VLAN Communication)
For VLAN traffic between switches, configure a trunk port:
Switch(config) interface gigabitEthernet 0/24 Switch(config-if) switchport mode trunk Switch(config-if) switchport trunk allowed vlan 10,20,30 Switch(config-if) exit
5. Deleting a VLAN
To remove a VLAN:
Switch(config) no vlan 20
6. Linux VLAN Configuration (Using `vconfig`)
On Linux, VLANs can be configured using:
sudo apt install vlan sudo modprobe 8021q sudo vconfig add eth0 20 sudo ifconfig eth0.20 up
7. Windows VLAN Tagging (PowerShell)
In Windows, use PowerShell to configure VLANs:
Set-NetAdapterAdvancedProperty -Name "Ethernet" -DisplayName "VLAN ID" -DisplayValue "20"
8. VLAN Security Best Practices
- Disable Unused Ports:
Switch(config) interface gigabitEthernet 0/5 Switch(config-if) shutdown
- Enable Port Security:
Switch(config-if) switchport port-security Switch(config-if) switchport port-security maximum 1 Switch(config-if) switchport port-security violation restrict
What Undercode Say:
VLANs are essential for modern network segmentation, improving security and efficiency. Whether on Cisco switches, Linux, or Windows, proper VLAN configuration ensures controlled traffic flow and reduces attack surfaces. Always verify settings, use trunking for inter-VLAN routing, and follow security best practices.
Expected Output:
A well-segmented network with isolated VLANs, verified via `show vlan brief` and show interfaces trunk.
URLs (if applicable):
References:
Reported By: Nasir Amin – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
