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!?
> >Make international calls for as low as $.04/minute with Yahoo! Messenger
> >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=15133&t=14961
--------------------------------------------------
FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
