From: Ronnie Angello (ronnie.angello@gmail.com)
Date: Fri Aug 31 2007 - 09:40:56 ART
VTP pruning does not remove the VLAN from the trunk like pruning manually
with the switchport trunk allowed vlan command. It just prevents flooded
traffic from going over trunk links where the traffic is not needed.
Manually pruning VLANs from trunks actually removes the STP instance for the
VLAN from the trunk as well.
On 8/31/07, Salau, Yemi <yemi.salau@siemens.com> wrote:
>
> Just to add to this in a lay-man language that I understand :-),
> vtp-pruning is an automated implementation of vlan-allowed list at trunk
> boundaries. Basically, you're allowing/denying tagged frames as they
> come in on that port depending based on vlan_id. But the good thing is,
> I don't need to accept a tagged frame with a vlan_id which doesn't exist
> on the Switch, so I "prune" such as it's coming into that trunk port.
> Could do this via vlan-allowed list, but vtp prunning is the automated
> variation of doing this.
>
> VTP Pruning is still useful these days, trust me.
>
> Many Thanks
>
> Yemi Salau
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> NET HE
> Sent: Friday, August 31, 2007 2:52 AM
> To: thomas.rader@freesurf.ch; ccielab@groupstudy.com
> Subject: RE: VTP Pruning
>
> Give you an example, then you will understand it.
>
> Let's say there are 3 switches linked by trunks in a VTP domain, switch1
> as
> vtp server, other 2 as vtp clients.
>
> Switch1 has host A1, B1, C1 connected to VLAN 1, 2, 3 respectively,
> switch2
> has hosts A2, B2, C2 connected to VLAN 2, 3, 4 respectively, and switch3
> has
> hosts A3, B3, C3 connected to VLAN 1, 2, 3 respectively
>
> After a period of silence, A1 is trying to ping A3, A1 first will send
> an
> ARP broadcast asking for MAC address of A3. If VTP pruning is not on at
> switch2, you will see ARP message on the trunk between switch1 and
> switch2,
> switch1 and switch3. But if VTP prunning is on at switch2, switch2 has
> already reported to switch1 saying that I don't have any hosts at VLAN
> 1,
> please don't send any VLAN 1 traffic to me. Therefore you will only see
> that
> ARP message on the trunk between Switch1 and Switch3, not the trunk
> between
> Switch1 and Switch2.
>
>
> Best Regards,
> Net (Xin) He
>
> >Hello,
> >
> >I've never really understood VTP Pruning.
> >
> >Sure I know that it reduces VTP traffic and is enabled using the "vtp
> >pruning" syntax, but I've never seen this deployed in any networks.
> >
> >Has anyone got any experiences with this or can share light on this
> matter
> >?
> >
> >Thanks, Thomas
> >
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-- Ronald Angello CCIE #17846
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