From: Joseph Ezerski (jezerski@xxxxxxxxxxxx)
Date: Wed Oct 10 2001 - 12:48:36 GMT-3
I might also add that you do not want a portfast type of technology on your
trunk links between switches. At least, in the Cisco world, turning on
Portfast bypasses MAXAGE and the Forward Delay timers and goes right into
Forwarding, thus effectively ignoring Spanning Tree. I would venture to say
that you might still have STP loops but are not noticing them, since
enjoying the blissful peace of non-convergence.
In a corrrectly functioning network, you should have NO topolgy changes
unless you added more switches, changed the root bridge, or changed the path
costs.
Do what Chris suggests. Set your root and secondary bridges. Don't leave
those to chance. It could be as simple as that. It is a good start. Then
work your way down from there.
I had an example where a Cat 3548XL, in a lab no less, that had a better MAC
and BID than my core 6509s and was assuming the duties of the root bridge
(this was before I set my root priorities). Everytime that switch was
rebooted or unplugged we had a convergence. Needless to say, it sucked,
until I set my root bridge priority to 0 and my secondary to 1. Now, the
only way someone can assume root is if they have a 0 priority and a better
MAC, which is highly unlikely. Add to that a newer feature from Cisco
called RootGuard that will eliminate even that slight chance.
I hope this helps.
-Joe
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Chris Allen
Sent: Wednesday, October 10, 2001 8:27 AM
To: Wright, Jeremy
Cc: ccielab@groupstudy.com
Subject: RE: BPDU/Topology Changes
Are you forcing Root and Secondary Bridge Elections??? If not I would....
Also you can make the network even more predictable and stable by manually
configuring port costs to force a certain path....
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Wright, Jeremy
Sent: Wednesday, October 10, 2001 10:18 AM
To: 'cisco@groupstudy.com'
Cc: 'ccielab@groupstudy.com'
Subject: BPDU/Topology Changes
My network recently was having a lot of topology changes. I then used
fastforwarding (Cabletron's version of port fast, and no I don't make the
decision on what hardware to purchase, I just configure) and it reduced the
number of changes tremendously. We are still having several per day, we have
about a 1000 users here. I'm running Sniffer with a filter on BDPU's and was
wondering if there were any suggestions on a better way to track the
topology changes down. Also, I would like to know what is the recommended
min/max number of topology changes. I realize it is specific to your network
but I just want to get a general feel. Thanks team
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