- Sincronize vlan creation between switches
- Its not a requirement of ethernet networks
- Doesn't define the broadcast domain
- it is for vlans administration, it has nothing to do with forwarding
VT1 & VT2 operation modeS
- VTP server: create vlans, advertises them (trunk links), installs vlans from other advertisements
- VTP client: no create vlans, advertises them (trunk links), installs vlans from other advertisements
- Transparent: create locally significant vlans, receive advertisement and forwards them,doesn't installs vlans from other advertisements
VTP configuration revision number
- Secuence number for the database
- Highest number wins
- Domain is synchronized when revision numbers are the same in each switch
- Wrong database can overwrite database in all switches if its revison number is the highest
- True for vtp servers and clients
- That's why vtp v1/v2 is rarely used in production
VTP PRUNNING
- Cuts down unnecasary broadcast, unicast, multicast
- Supported in server and client mode
- Vlans 2 -1001 are prune eligible
- Vlans not in the prune list can not be prunned
VTP AUTHENTICATION
- Used for vtp updates validation
COMMANDS
- show vtp status:
- which versions supports
- which version is running
- vtp domain name
- vtp operation mode (server,client, transparent)
- Number of existing vlans
- Let me see the hash
- vtp domain name: set the domain name
- vtp mode transparent :
- Change the operation mode of the switch to transparent, it doesn't delete the vlans created
- Change the revision number to 0, which means it doesn't listen for updates to install
- To forward advertisements it has to be in the same vtp domain
- vtp pruning:
- enable vtp pruning, only for clients and servers
- show interfaces prunning
- vtp password : sets the update password in clients and servers
- show vtp password : Checks if password match i all switches
TROUBLESHOOTING
- Transparent mode will not forward advertisements for vlans not created in its local database
- Transparent mode will not forward advertisements when it doesn't have the same domain name
- When a switch doesn't receive a reply for a pruning request, it will install all the vlans in its datbase
- It happens when the trunk port is connected to a non cisco device, cause vtp is cisco propietary
- it can be solve manually indicating the vlans allowed in that trunk with the command "switchport trunk allowed vlans"
- When using prunning make sure there is no transparent switches in the domain
- Sometimes authentication is broken even the passwords are the same
- This happens cause the hash is different (show vtp status), this is because the hash generation depends on the revision number
- Domain names are case sensitive
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