Why use Vlan

  1. Reduce CPU
  2. Reduce security risk by reducing hosts that receive copies off frames that swiches flood
  3. Imporve security ofr hosts that send sensitive data by keeping host separate
  4. Flexibiolty
  5. Solve problem faster
  6. Reducce workload for STP

ISL and 802.1q – insert extra 4byte (12bit ) 802.1q vlan header into the original frames ethernet header. 2^12 = 4,096 4096 max vlans

Extended range VLAN ID – 1006-4096

VTP – VLAN Trunking Protocol

  1. Consistent VLAN configuration across all switches in the network
  2. VLAN trunking over mixed networks, such as ethernet to ATM LANE or even FDDI
  3. Accurate tracking and monitoring of VLANS
  4. Dynamic reporting of added VLANSs to a ll switches in the VTP domain
  5. Adding VLANs using Plug and Play.
  6. VTP server up to 1-1005 vlan id
  7. VTP transparent same as VTP off but sends VTP out interface


  1. Range (2-1001) (1002-1005 reservered)
  2. VTP synchronization every
  3. VTP sync to the highest rivision number in the VLAN configuraiton database
  4. VTP configuration must match
    1. The link between the switches be operating same VLAN trunk
    2. Two switch case sensitive VTP domain must match
    3. If configured case sensitive VTP password must match
  5. VTP sent every 5 minutes
  6. VTP mode, VTP domain, VTP password, VTP pruning, VTP version
  7. Vlan.dat file in flash