Cisco now prefer to implement MVPST. It allows a single spanning tree
instance to run for multiple VLAN. So you reduce the CPU charge caused by a
large number of VLAN created on your network but you still have a
"security" issue by having different ST instance running for each group of
VLAN. This runs of 802.1Q links only
Hope it helps
At 08:07 AM 8/8/2001 -0400, Picciani Francesco Saverio wrote:
>I would say that if, for any reason, some V-LAN have spanning tree problem,
>during the convergence time of the spanning tree algorithm related to that
>V-LAN, other V-LANs continue to work even if they share the same trunk.
>
>-----Messaggio originale-----
>Da: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED]]
>Inviato: martedl 7 agosto 2001 20.02
>A: [EMAIL PROTECTED]
>Oggetto: Re: R: vtp, spanning tree [7:14961]
>
>
>At 02:53 PM 8/7/01, Picciani Francesco Saverio wrote:
> >I thing that the main benefit of having per-VLAN spanning tree is that a
> >problem on a VLAN does not impact the other VLANs also if they lay on the
> >same ISL trunk.
>
>If the VLANs share a trunk, then they do affect each other. For example, if
>one VLAN is experiencing a broadcast storm or some other problem related to
>excessive traffic, that problem could affect other VLANs on the same trunk.
>The trunk is shared bandwidth.
>
>But with per-VLAN spanning tree, you could have two trunks and divide up
>which VLANs travel each trunk as first priority.
>
>Without per-VLAN spanning tree, if you had two trunks between two switches,
>one of the trunks would be in the blocking state (or you would have a
>loop). With standard spanning tree, there's no load sharing across
>redundant links.
>
>Maybe that's what you were saying, but I just wanted to add on a bit.
>
>Priscilla
>
>
> >-----Messaggio originale-----
> >Da: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED]]
> >Inviato: lunedl 6 agosto 2001 20.05
> >A: [EMAIL PROTECTED]
> >Oggetto: Re: vtp, spanning tree [7:14961]
> >
> >
> >At 02:13 PM 8/5/01, Cisco Troubleshooter wrote:
> > >can any body tell,
> > >
> > >why we need spanning tree protocol per vlan
> >
> >If you have a large, switched network, all the switches are in the same
> >spanning tree. Converging the spanning tree can take a long time. In
> >addition, traffic flow may not be optimized. The selection of the root
> >bridge and which interfaces are blocking might not be optimized for all
the
> >applications and devices in the large, switched network.
> >
> >With per-VLAN spanning tree, each VLAN becomes a single spanning tree with
> >its own root bridge and own set of blocked ports. This way you can
optimize
> >traffic flow and reduce the amount of work to converge to a spanning tree.
> >It's somewhat analogous to dividing a routed network into areas or
> >autonomous systems.
> >
> >Also, at least with Catalyst 1900 switches, if you allow all VLANs to
> >travel across both trunks, you will have a loop. If you don't configure
> >per-VLAN spanning tree, you will have a broken network. You would think
> >spanning tree would just work around this problem, but it doesn't seem to
> >when VLANs are configured.
> >
> >
> > >and vtp why it is needed what purpose it serves
> >
> >VTP is a management protocol that allows switches to share information
> >about VLAN names and IDs. It reduces configuration because you can
> >configure VLAN names and IDs on just one or two server switches. The rest
> >of the switches act as clients and pick up the info when they boot.
> >
> >By default, the switches do not keep track of which switches have which
> >VLANs configured, however. I disagree with the other responder who said
VTP
> >reduces bandwidth usage on links and switches. It's VTP pruning that does
> >that.
> >
> >If you configure VTP pruning, then an added VTP message gets sent. The
> >added message includes VLAN membership information. With VTP pruning, the
> >switches become a bit smarter and do not forward traffic for a VLAN across
> >a link or to a switch that has no ports in that VLAN. This must be
> >configured. Without pruning, VTP just shares info about VLAN names and
IDs.
> >
> >Priscilla
> >
> >
> > >thnx in advance
> > >
> > >jd
> > >
> > >__________________________________________________
> > >Do You Yahoo!?
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> > >http://phonecard.yahoo.com/
> >________________________
> >
> >Priscilla Oppenheimer
> >http://www.priscilla.com
>________________________
>
>Priscilla Oppenheimer
>http://www.priscilla.com
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=15259&t=14961
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