VLANs

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VLANs

• By Mahdi Nasereddin Ph.D.

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VLAN?

• A Virtual Local Area Network is a logical
  grouping of network users and resources connected
  to administratively defined ports on a switch.

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Why use VLANs?

• Layer 2-switched networks are flat
• One big broadcast domain
• Flexibility
• Security
• Anybody connected to the physical network could
  access network resources.
• With VLAN, Administrator control the ports

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Flat Network
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Flexibility
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Flexibility
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VLAN Membership

• Static VLAN
• Typical way of creating VLAN
• Ports are assigned by the administrator
• Dynamic VLAN
• Automatic port assignment (you have to create a
  MAC lookup table)
• Uses Intelligent Management Software (Example
  Ciscos VMPS)

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Link Types in a switched Environment

• Access links
• Part of one VLAN
• Devices attached to access links dont realize
  that they are connected to a VLAN
• In order to communicate with devices on other
  VLANs, the packets have go through a router

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Link Types in a switched Environment (cont.)

• Trunk links
• Carry multiple VLANs
• Used to connect switches to other switches,
  routers, or servers.
• Runs on fast or gigabyte Ethernet only
• Contain a default VLAN used if the trunk link
  fails

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Trunk Link