[c-nsp] VTP Pruning

[Tim Stevenson]

Yes, this just prunes unneeded flood traffic, it does nothing to prevent 
the advert of the VLAN database.

Yes another argument for manual vlan configuration & manual vlan trunk 
pruning via allowed lists... ;)

Tim

At 03:37 PM 3/16/2005, MADMAN declared:


>Bruce Pinsky wrote:
>
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> > Dave Temkin wrote:
> > | Does anyone have a pointer to a doc that shows *how* VTP Pruning 
> works?  I
> > | definitely know *what* it does, but none of the docs say how it 
> determines
> > | whether or not a VLAN is in use...
> > |
> >
> > I haven't found a public one that I can point you at.
> >
> > | I had an issue years ago where even if there was an active port in a
> > | VLAN, it got pruned because the CAM entry fell out after awhile.  This
> > | broke things because it was in a one-way broadcast type environment
> > | (market data).  The general understanding is that if a port is active in
> > | that VLAN that it shouldn't be pruned....  But as I just stated, that
> > | wasn't the case in the past - and I'm not sure if that was a bug or if it
> > | was how it was intended to work....
>
>    One thing VTP pruning does not do is keep a VLAN from being announced
>at all.  While beta testing the HWIC I mentioned this would be nice
>since the HWIC and other low end switches supports a limited number of
>spanning tree instances.  When you connect a trunk you get an error
>message for every STP instance over the alloted max.
>
>    Dave
> > |
> >
> > According to the specs I've read, the pruning function is only notified of
> > the following events for local VLAN access ports:
> >
> > - - Link state change of an access port
> > - - Port state change of an access port (i.e. admin status)
> > - - STP forwarding state change of a VLAN on access ports
> > - - VLAN membership change of an access port
> > - - Management VLAN changes
> >
> > So having a valid CAM entry on a port in a VLAN does not appear to be one
> > of the criteria for considering that a VLAN is "active".
> >
> > - --
> > =========
> > bep
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>
>--
>David Madland
>CCIE# 2016
>Sr. Network Engineer
>Qwest Communications
>612-664-3367
>
>"Emotion should reflect reason not guide it"
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Tim Stevenson, tstevens at cisco.com
Routing & Switching CCIE #5561
Technical Marketing Engineer, Catalyst 6500
Cisco Systems, http://www.cisco.com
IP Phone: 408-526-6759
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