[c-nsp] VTP Pruning point .

[Murphy, William]

Pruning is handled by VTP messages...  When there are no active ports in a particular VLAN VTP tells the upstream switch to stop flooding traffic on that link.  Spanning tree is still functional for all the VLANs but uncessary traffic is pruned back...

________________________________

From: cisco-nsp-bounces at puck.nether.net on behalf of Ibrahim Abo Zaid
Sent: Wed 12/5/2007 2:27 AM
To: Darryl Dunkin
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] VTP Pruning point .



Dear Darry

so prunuing is applied to traffic-forwarding only and all switches knows all
the domain VLAN but the traffic is forwarded for the active VLANs only .

so if VTP updates advertises all domain VLANs how the switches knows which
VLAN is active and which aren't ? via STP BPDUs for PVSTP mode or how ?
best regards
~Ibrahim


On Dec 5, 2007 5:27 AM, Darryl Dunkin <ddunkin at netos.net> wrote:

> Pruning is not to prune the configuration, but to prune the forwarding
> of traffic between switch ports (VLANs forwarded on the trunk itself)
> when that VLAN is not active on the neighboring switch. Even if the
> traffic is pruned, the switches will still know about all VLANs in the
> domain but not receive traffic for pruned VLANs.
>
> An example 'show trunk' on CatOS appears like this when VLANs are pruned
> (2-5 are pruned on port 2/50 in this case).
>
> Port      Vlans allowed and active in management domain
> --------
> ---------------------------------------------------------------------
>  2/50     1-9
>
> Port      Vlans in spanning tree forwarding state and not pruned
> --------
> ---------------------------------------------------------------------
>  2/50     1,6-9
>
> The configurations are synced via VTP however and both switches know
> about all 9 VLANs.
>
> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Ibrahim Abo Zaid
> Sent: Tuesday, December 04, 2007 18:22
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] VTP Pruning point .
>
> Dears
>
> i have a question about VTP Pruning which is used to optimize broadcast
> forwarding over trunk links in switched networks
>
> i think before doing so the switches needs to synchronizes VLAN
> configurations between each other so i think VTP update
> messages shall contain ACTIVE VLANs (VLANs which have active ports @ the
> switch) instead of ALL-DEFINED VLANs
>
> and that truns Trunks from ALL-VLANs members state to ACTIVE-VLAN state
> means it would be members of Active VLANs only not All domain VLANs
>
> i couldn't find any article verifies that point so if any one has an
> idea is
> that true or something else is used i will be appreciated for any help
> :)
>
> best regards
> --Abo Zaid
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