what is the point for using vtp?

Answered Question
Nov 15th, 2008

hi every body!

I understand in older ios vesrion, one has to define vlans on switch before assiging the ports to respective vlans. Here vtp saves the one from defining vlans on each switch.

However in new ios i find even if we dont define vlans on the switch and assigns the ports to respective vlans, vlans are automatically created. In such situation why should one use vtp as one assigns the ports to respective vlans, vlans would be created automatically by the new ios?

thanks a lot!

I have this problem too.
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Correct Answer by Massimo Baschieri about 8 years 2 months ago

Things are not always so simple, there are cases where you have transit switches that doesn't host ports for some specific vlans, since you need to create vlans through all the path from core to access in order for the traffic to flow, you need vtp or manually create vlans on transit switches.

Bye,

Tosh.

Correct Answer by allan.thomas about 8 years 2 months ago

Essentially VTP reduces administration in a switched network. When you configure a new VLAN on the designated VTP server, the VLAN is distributed through all switches in the

domain.

As you mentioned this reduces the overall need for configuring the same VLAN everywhere. However, there are situations where broadcast will be flooded in a VLAN, and if the VLAN is allowed across all trunk ports, then so will the broadcast.

A feature of VTP is VTP pruning which will prune this traffic if there are no members assigned to this VLAN at edge for example. It will only be flooded to switches where the switchports with active port member in that given VLAN.

In your case your are effectively creating and duplicating all the VLANs across your network, which is effectively the same as the VTP Transparent mode, it will be necessary to manually add or clear unwanted VLANs from your trunk ports.

I find that Transparent mode gives you more control over where you extend your broadcast domains. In such sitations you are specifically required to configure the vlan on switches.

Therefore transparent mode is better suited to static enviroments where you are not constantly moving ports between vlans across access switches.

Hope this helps.

Allan.

Pls rate helpful posts.

Correct Answer by e.claveau about 8 years 2 months ago

Using VTP also makes life easier when configuring core and distribution switches with many trunks, any new VLAN's are propagated between all the core and distribution switches in the VTP domain.

Correct Answer by lejoe.thomas about 8 years 2 months ago

The primary purpose for VTP is to propagate VLAN information configured on one switch to all the remaining switches in the network. This allows for central control. Even when using VTP, only vlan information (not ports assigned to the VLAN on one switch) is propagated across all the other switches, one must still go and specify which ports will be part of a VLAN on each switch.

So ,if we must go and add ports on each switch to respective VLANs, then why use VTP? it avoids VLAN misconfigurations such as wrong VLAN names,types etc.

HTH

Lejoe

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Correct Answer
lejoe.thomas Sat, 11/15/2008 - 19:45

The primary purpose for VTP is to propagate VLAN information configured on one switch to all the remaining switches in the network. This allows for central control. Even when using VTP, only vlan information (not ports assigned to the VLAN on one switch) is propagated across all the other switches, one must still go and specify which ports will be part of a VLAN on each switch.

So ,if we must go and add ports on each switch to respective VLANs, then why use VTP? it avoids VLAN misconfigurations such as wrong VLAN names,types etc.

HTH

Lejoe

Correct Answer
e.claveau Sat, 11/15/2008 - 19:49

Using VTP also makes life easier when configuring core and distribution switches with many trunks, any new VLAN's are propagated between all the core and distribution switches in the VTP domain.

Correct Answer
allan.thomas Sat, 11/15/2008 - 20:08

Essentially VTP reduces administration in a switched network. When you configure a new VLAN on the designated VTP server, the VLAN is distributed through all switches in the

domain.

As you mentioned this reduces the overall need for configuring the same VLAN everywhere. However, there are situations where broadcast will be flooded in a VLAN, and if the VLAN is allowed across all trunk ports, then so will the broadcast.

A feature of VTP is VTP pruning which will prune this traffic if there are no members assigned to this VLAN at edge for example. It will only be flooded to switches where the switchports with active port member in that given VLAN.

In your case your are effectively creating and duplicating all the VLANs across your network, which is effectively the same as the VTP Transparent mode, it will be necessary to manually add or clear unwanted VLANs from your trunk ports.

I find that Transparent mode gives you more control over where you extend your broadcast domains. In such sitations you are specifically required to configure the vlan on switches.

Therefore transparent mode is better suited to static enviroments where you are not constantly moving ports between vlans across access switches.

Hope this helps.

Allan.

Pls rate helpful posts.

Correct Answer
Massimo Baschieri Sat, 11/15/2008 - 23:29

Things are not always so simple, there are cases where you have transit switches that doesn't host ports for some specific vlans, since you need to create vlans through all the path from core to access in order for the traffic to flow, you need vtp or manually create vlans on transit switches.

Bye,

Tosh.

Davy Ad Mon, 11/17/2008 - 05:22

But make sure other switches are in Client mode to avoid mismatched

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