From: Chris Larson (clarson52@xxxxxxxxxxx)
Date: Thu Aug 29 2002 - 18:31:00 GMT-3
This has gone round a lot lately. The only way to ensure a Cisco switch
never becomes root is to disable spanning-tree.
Root-gaurd is not an option. It may keep down-level switches on a particular
port from becoming root, but if the switch hosting the root-gaurd feature
breaks then the down-level switch would become root.
Same with priority, if you only have one switch it is root period. If there
are multiple switches and the switch or switches that have the lower
priority break then your switch with 65535 still becomes root.
The only way to ensure a switch NEVER becomes root is to disable spanning
tree.
----- Original Message -----
From: "Chris Butler" <butlerc@thielenlaw.com>
To: <OuDavid.Zhang@gs.com>
Cc: <ccielab@groupstudy.com>
Sent: Thursday, August 29, 2002 2:13 AM
Subject: Spanning Tree Root Election-How to stop it.
> David,
>
> You got it right in the first one. The higher the priority, the less
> likely that a switch will become the root bridge. The best way to avoid
> beoming root bridge, ie...you are still running spanning tree, is to make
> the priority has high as possible. In this case 65535.
> The opposite would be the case if you wanted to control the spanning tree
> root election. The root command never did work very successfully in the
> 5000 series, so the best way to control root election is to make him 8192,
> and your back up 16384. The remaining switches can just stay at the
> default of 32768.
> Good job,...don't doubt yourself next time...
>
> Chris
> > Hi,
> >
> > Please help me with the answer for this question: Ensure that a
> > Catalyst 5000 switch never becomes the root bridge for a given vlan.
> >
> > I see two possible answers because I find the question ambiguous. Does
> > it mean 'the vlan can still run spanning tree without ever becoming the
> > root', or 'the vlan does will no longer run spanning tree'?
> >
> > 1. Set the spantree bridge-priority for the vlan to the highest
> > possible value.
> > !
> > set spantree priority 65535 <vlan#>
> > !
> >
> > 2. Disable spantree altogether for the vlan.
> > !
> > set spantree disable <vlan#>
> > !
> >
> > Thanks.
This archive was generated by hypermail 2.1.4 : Sat Sep 07 2002 - 19:48:42 GMT-3