1. VLAN Cisco (Router/Switch)
Dr. Young
Cal Poly Pomona

2. Definition Virtual Local Area Network Logical group of network users
Associate with ports on a switch
Unique ID and NAME
VLANs could span multiple switches

3. Problems with flat network
Broadcast domain become too large
No security control for individual switch ports
Inflexible because subnets are created only with addition of routers
Net B
Net C
Net A
Router
A flat network
Net D

4. What does VLAN do?
Create smaller broadcast domains by grouping users according to
Location
Department
etc
Improve security by preventing anyone in the same LAN from monitoring the network traffic (eavesdropping)

5. What does VLAN do?
Increase flexibility and scalability by letting system administrators to create virtual subnets without adding routers

6. Broadcast in flat network
Receive
Switch
Router
Switch
BROADCAST
Switch

7. Broadcast in VLAN VLAN A VLAN B VLAN C RECEIVE Router BROADCAST Switch

8. Routing between VLAN Switches do not route data between VLANs
Routing has to be done in routers, the same way as with ordinary subnets