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VLAN Cisco (Router/Switch). Dr. Young Cal Poly Pomona. 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. Problems with flat network. Broadcast domain become too large
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VLANCisco (Router/Switch) Dr. Young Cal Poly Pomona
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
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
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)
What does VLAN do? • Increase flexibility and scalability by letting system administrators to create virtual subnets without adding routers
Receive Receive Receive Receive Receive Receive Receive Receive Broadcast in flat network Switch Router Switch BROADCAST Switch
RECEIVE RECEIVE Broadcast in VLAN VLAN A VLAN B VLAN C Switch Router Switch BROADCAST Switch
Routing between VLAN • Switches do not route data between VLANs • Routing has to be done in routers, the same way as with ordinary subnets