1. Overview
   1. VTP advertises the VLAN ID, VLAN name, and VLAN type and state for each VLAN.
   2. 3 Version - VTPv1, VTPv2 & VTPv3
   3. NOT advertise relationship Port / VLAN
   4. ONLY supported in Trunk Port
   5. Server & Client save VLAN updates in vlan.dat (not NVRAM)
   6. Prunning ONLY on normal range vlans 1-1005
   7. Cisco Proprietary
2. Versions
   1. VTPv1
      1. default VTP version supported and active on enterprise IOS-based switches
      2. Support only normal-range VLANs
   2. VTPv2
      1. Support for Token Ring VLANs Type
      2. Support for unknown Type-Length-Value (TLV) records
      3. Optimized VLAN database consistency checking - Skip checking
   3. VTPv3
      1. two server types: primary and secondary
         1. Primary : only is allowed to modify VTP domain contents ; Max 1 per domain
         2. Secondary : serve as backup - take ownership if primary fail
      2. password storage and usage
         1. Stored Encrypted
      3. Distribute full range of VLANs including Private VLANs
      4. off mode : don't participate and discard VTP message
3. Modes
4. commands
   1. (G) vtp domain {{ domain }}
   2. (G) vtp password {{ pwd }}
   3. (G) vtp mode {{ mode }}
   4. (G) vtp version {{ version }}
   5. (G) vtp mode off
   6. (IF) no vtp
   7. (G) do vtp primary
   8. show vtp status
   9. show vlan brief
   10. show vtp
       1. counters
       2. devices
       3. interface
       4. password
       5. status
5. Messages Types
   1. Summary Advertisement
      1. Sent by server & clients every 5 minutes and after each modification to the VLAN db.
      2. Carry information about:
         1. VTP domain name
         2. Revision number - Higher Wins
         3. ID of the last updater & timestamp of the last update
         4. of Subset Advertisement messages that optionally follow this Summary Advertisement.
         5. MD5 sum over the contents of the VLAN db, and the VTP pwd - only this type carry MD5
   2. Subset Advertisement
      1. Send by server & clients after modifying the VLAN db.
      2. Carry full contents of the VLAN db.
   3. Advertisement Request
      1. Sent by server & clients to request their neighbors the complete VLAN db or a part of it.
   4. Join Messages
      1. Originated by each server & client periodically every 6 seconds if VTP pruning is active.
      2. Contains a bit field for each VLAN in the normal range indicating if is active or pruned.