🖧 VLAN (Virtual Local Area Network)

---

🧠 Top 5 Key Points

1. Logical Network Segmentation:
   VLANs divide a physical network into multiple logical networks, improving management and security.

2. Improved Security:
   Devices in different VLANs cannot communicate unless explicitly allowed via a router or Layer 3 switch.

3. Reduces Broadcast Domains:
   Each VLAN is its own broadcast domain, minimizing unnecessary traffic.

4. Better Management:
   Departments (HR, Sales, IT, etc.) can be grouped into different VLANs without changing physical cabling.

5. Requires VLAN Tagging (802.1Q):
   VLAN information is carried between switches using 802.1Q trunking.

---

⚙️ Technical Notes

Feature	Description
OSI Layer	Layer 2 (Data Link)
Standard	IEEE 802.1Q
Device Type	Managed Switch or Layer 3 Switch
VLAN Range	1–4094
Default VLAN	VLAN 1

---

🧰 Packet Tracer VLAN Lab

🎯 Goal:

Create three VLANs (10, 20, 30) on a switch, assign PCs to them, and verify connectivity.

---

🖥️ Network Topology

           +------------------------+
           |        Switch (S1)     |
           +------------------------+
             |      |      |
           PC1    PC2    PC3

---

VLAN Plan

VLAN ID	VLAN Name	Department	Connected PC	IP Address
10	HR	HR Dept	PC1	192.168.10.10
20	SALES	Sales Dept	PC2	192.168.20.10
30	IT	IT Dept	PC3	192.168.30.10

---

🪜 Configuration Steps

🔹 On the Switch (S1)

enable
conf t
vlan 10
 name HR
vlan 20
 name SALES
vlan 30
 name IT
exit

🔹 Assign Ports to VLANs

Assume:

• PC1 → FastEthernet 0/1

• PC2 → FastEthernet 0/2

• PC3 → FastEthernet 0/3

interface range fa0/1
 switchport mode access
 switchport access vlan 10
exit

interface range fa0/2
 switchport mode access
 switchport access vlan 20
exit

interface range fa0/3
 switchport mode access
 switchport access vlan 30
exit

---

🔹 Verify VLAN Configuration

show vlan brief

➡ Confirms VLAN IDs, names, and assigned ports.

---

🔹 Set IP Addresses on PCs

PC	VLAN	IP Address	Subnet Mask
PC1	10	192.168.10.10	255.255.255.0
PC2	20	192.168.20.10	255.255.255.0
PC3	30	192.168.30.10	255.255.255.0

(Configure via Desktop → IP Configuration tab in Packet Tracer)

---

💡 Testing

Try pinging between PCs:

• PC1 → PC2 (should fail — different VLANs)

• PC1 → PC3 (should fail)
  ✅ Same VLAN pings succeed (if trunk and router configured later).

---

🚦 Optional: Inter-VLAN Routing

To allow communication between VLANs, use a Router-on-a-Stick configuration:

• Create subinterfaces on a router.

• Use 802.1Q encapsulation to handle multiple VLANs on one trunk port.

---

🧠 Learning Summary

Concept	Description
VLAN	Virtual LAN — separates network logically
Benefit	Security, scalability, and efficiency
Broadcast Domain	Each VLAN = 1 broadcast domain
Trunk Link	Carries multiple VLANs (802.1Q tagging)
Router on a Stick	Enables inter-VLAN communication

---

🗺️ Teaching Tip

“VLANs let you separate a single switch into multiple smaller virtual switches — like dividing one big office into smaller secure departments without adding new hardware.”