VTP pruning

[sivam siva]

HI 

What is the difference between  VTP pruning & VLAN pruning in trunk, both are configured by manually and both features prevents the VLAN frame in trunk, then what is the difference ?

Thanks in advance 

[Georg Pauwen]

Hello,

not sure what you mean...VLAN pruning is done through VTP. Or do you mean 'trunk allowed vlan' vs VLAN pruning ?

[sivam siva]

Yes

Alex explained  the concepts that I can understand, my question is both pruning VLAN through VTP or on the trunk itself ( ex: sw tr allowed vlan x) need to be configured manually , 

So what is the difference ? What VTP simplifies the administrator overhead in this scenario.

Thank you 

[Alex Pfeil]

VLAN trunking protocol is a Cisco proprietary way of managing VLANs across a network. VTP pruning is a feature of VTP that will automatically remove VLANs from trunks on switches where the VLAN is not used.
VLAN pruning would be the practice of manually allowing specific VLANs across a trunk with the switchport trunk allowed vlan command.
The best practice is to set all switches to VTP mode transparent and manually add all of the VLANs that are needed on each device. You then trunk each device and allow the necessary VLANs.

Please mark helpful posts.

[haggittmark@tm-america.com]

I feel Alex's post is actually the best complete answer.

Rising Star is a Shining Star

[Georg Pauwen · Accepted solution]

Hello,

as Alex explained, VTP pruning is a lot easier to configure, since you only need to enable it on the VTP server. In addition, the 'switchport trunk allowed' command is static, that is, should there be a port connected to a Vlan that you actually want to traverse the trunk, you will have to manually change that, while VTP would adjust dynamically...

[sivam siva]

Got it ,thank you 

[paul driver]

Hello
I personally would NEVER use dynamic vtp pruning, I have seen instances even when a remote switch has had ports related to a specific vlan or even allowed to traverse the trunk vtp pruning has dynamically removed it and caused outage

Manually pruning your vlans is in my opinion the best option - It provides a total controllable approach to vtp pruning on the trunks

Enabling vtp pruning dynamically it is the easiest option to deploy granted but I have found it not deterministic enough to trust which I have found to my cost.

[haggittmark@tm-america.com]

I agree.  A year ago we when to 'allowed vlan' per interface.  However, I have an issue that is just creeping up.  I will repost as a new issue, but it would be really cool if you could comment, Paul. Thanks!  The situation is that I have lost the benefit of the 'ip helper-address'. 

[haggittmark@tm-america.com]

The name of the new post is 'Allowed VLAN' pruning, 'ip helper-address', and DHCP.

[paul driver]

Hello

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haggittmark@tm-america.com wrote:
 I have lost the benefit of the 'ip helper-address'. 

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Can you elaborate please?

[haggittmark@tm-america.com]

Is the only way to forward DHCP requests to use Cisco's proprietary VTP 'ip helper-address'?