VLANs (Virtual Local Area Networks)
Master VLAN configuration, trunking, and network segmentation for enhanced security and performance
What are VLANs?
VLANs (Virtual Local Area Networks) logically segment a physical network into multiple broadcast domains, allowing devices to communicate as if they were on the same physical network segment regardless of their physical location.
Key Concepts:
- VLAN ID: Unique identifier (1-4094) for each VLAN
- Access Ports: Untagged ports assigned to a single VLAN
- Trunk Ports: Tagged ports carrying multiple VLANs
- Native VLAN: Default VLAN for untagged traffic on trunk ports
- 802.1Q: IEEE standard for VLAN tagging
VLAN Benefits:
Security Isolation
Separate sensitive data from public access
Performance
Reduce broadcast domains and network congestion
Management
Logical grouping independent of physical location
Scalability
Easy to add/remove devices from VLANs
VLAN Types & Examples
VLAN 1
Default VLAN
Untagged traffic (VLAN 1)
VLAN 10
Sales VLAN
Sales department devices
VLAN 20
Engineering VLAN
Engineering workstations
VLAN 30
Guest VLAN
Visitor network access
VLAN 99
Management VLAN
Network device management
💡 Quick Tip
VLAN 1 is special:
- Default VLAN for all ports
- Cannot be deleted
- Often used as native VLAN
- Security risk if not properly managed
Port Assignment Visualization
Fa0/1ACCESS
VLAN: 10 | Device: Sales PC
Fa0/2ACCESS
VLAN: 10 | Device: Sales Printer
Fa0/3ACCESS
VLAN: 20 | Device: Eng Workstation
Fa0/4ACCESS
VLAN: 30 | Device: Guest Device
Gi0/1TRUNK
VLAN: All | Device: Core Switch