Wednesday, September 30, 2015

VTP notes


  • In VTP v1 & v2 change mode to transparent to reset revision number
  • Vlan state(Active/Suspended) is advertised by VTP. Shutting down a vlan is locally significant to the device the the command was applied
  • A transparent switch forwards VTP packets only if they match it's own configured VTP domain
  • DTP negotiation between two switches requires VTP domain name to match between switches
  • If a switch doesn't receive a VTP pruning response on a port, as a fallback mechanism, it doesn't prune any vlan on that port. As a consequence it requests all vlans from it VTP neighbors, which actually cancels VTP pruning operation. This is true for edge ports too. As a solution either disable VTP on that port(VTPv3) or manually set allowed vlan list. 
  • Don't use VTP pruning on a VTP domain that includes transparent switches. Transparent switches only forward VTP packets and don't take part in the negotiation, leading to traffic blackholes
  • By default all standard vlans are included in the prune eligible list
  • VTP domain name is case sensitive
  • In transparent mode vlans are stored in running config
  • In client/server mode vlans are stored in vlan database
  • In VTPv3 you have to define a primary server in exec mode in order to be able to alter the vlan database
  • In VTPv3 you need to disable VTP pruning in order to advertise the extended vlan range
  • Useful debug command: debug sw-vlan vtp events

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