15 - VTP - Overview Flashcards
What is VLAN Trunking Protocol = VTP ?
It manage the addition, deletion, and renaming of VLANs from a central point.
This is done by making changes on 1 switch and in turn other switches copy from that 1 switch.
What problem does it solve ?
Configuring VLAN and VLAN trunking for large networks with many interconnected switches can be a very difficult task.
VLAN Trunk Protocol (VTP) is a protocol created by Cisco to create and manage VLANs for a large network with many interconnected switches and to maintain consistency throughout the network. In other words, switches use VLAN trunking protocol (VTP) to communicate among themselves about VLAN configuration.
An Example of how VTP works
What is “revision Number” mean in VTP
switch 1 ———— vlan 10 added
switch 2 ———— this copies it
switch 3 ———— so does this
Rev 0 is start -
Both switch 2 & 3 start on Rev 0, changes to rev 1 as it copies the vlan update
What are the VTP Modes ?
Just the names -
- Server ( Default on switch )
- Client ( listens - can not make any changes at all )
Transparent ( similar to turning it off )
VTP Mode - Server
- what does it do ?
- what are its features ?
Server ( Default on switch )
- you can change Vlan config on the switch
- it sends Vlan VTP updates to other switches
- it receives Vlan VTP updates from other switches
- it allows you to saves Vlan configurations
VTP Mode - Client
- what does it do ?
- what are its features ?
- cannot change clan configuration
- does not recive, does no send VTP updates
- Does not allow you to save vlan configurations
VTP Mode - Transparent
- what does it do ?
- what are its features ?
- you can change Vlan config on the switch
- it sends Vlan VTP updates to other switches ( passes through )
- Does not change its own config, when it receives VTP updates
- it allows you to saves Vlan configurations
If there is a Transparent mode switch between 2 Server mode switch - what will happen ?
Note : if two switches are on server mode & have in the middle of them a Transparent mode switch that connects both of them together.
Then the transparent mode being in the middle will happily pass info on, which willl effect other server mode switch.
In VTP what is - VLAN Pruning ?
VLAN Pruning is explained below -
Switch 1 - ( vlan 10, 20, 30 )
Switch 2 - VTP MEans switch 2 & 3 will copy
Switch 3 - but switch 3 has no ports using vlan 30, so it will send updates to switch 2 (only sw2) that it doesnt require broadcast from vlan 30
The problem is Vlan pruning only works on Server mode. Not on client or Transparent mode.
What is VTP Domain name ?
This is important to VTP
Only switches which have the same “ VTP domain name” will be allowed to copy & add Vlan details.
VTP domian name adds a little protection:
If the rouge switch is added to our network and does not have the same VTP domain name then it is ignored.
If we plug a rouge switch with a high Revision number is added, what will happen ?
- All the switches will copy the new vlan database from the rouge switch
- Vlans that do not exist on the rouge switch will be erased. e.g if vlan 10 doesnt exit it will erase it.
- All the interfaces switchported to vlan 10 will become amber light.
- why ? becuase it will remain under vlan 10 but since vlan 10 does not exist it will not work.
If the config from a switch is wiped then added to the network what can happen ?
- switch confige is wiped - it can still cause this problem.
because VTP revision survive configuration resets.
Vlans survives configuration resets.
When VTP deletes switch ‘E’ vlans.
We restore the switch ‘E’ config from back up.
What happens ?
Soon as Switch ‘E’ connects to the network, the network switches VTP revision is higher, so it will deletes switch ‘E’ vlans again.
Only way is to manually configure the Vlan on switch’E’.
which will update the VTP revision with the new info
