[ednog] Anyone deploying MSTP and/or RSTP as alternatives to spanning tree?

Laura Grill-Kristoff laura at rocky.ittns.northwestern.edu
Fri Apr 29 10:13:11 EDT 2005

On Thu, Apr 28, 2005 at 03:44:47PM -0500, Nicola Foggi wrote:
> <snip>
> We ran across the limited # of spanning tree instances a couple of
> times unfortunately...  we haven't looked at MST yet, but we did end up
> manually pruning the vlan's off the trunked interfaces for vlans that
> were not in use which solved the # of spanning tree.. 

I recall that we tried manually pruning to get around the spanning tree
instances as well, but pruning didn't remove the number of VLANS on the
switch... just the ones that were allow to be forwarded on the trunk port.

In our case at least, we were using VTP with our core switches as the servers
and our access layer switches as the clients.  This caused all VLANS in the
domain to be created on the access layer switches.. and that's how we ended
up with too many instances on the access layer switches.  What finally solved
our problem was to change to transparent mode which makes each switch
independent (basically manually setting the VLANS in the config of the

> it also solved a
> problem we were having with the cam table's filling up and caused
> multicast reliability problems...  

Hmm.. I don't think we saw that one.  We had problems with flooding of
multicast on our access switches, but it was due to Windows hosts with 
bridging turned on... or I guess the way the Cisco dealt with the topology
change notifications it received.

Laura Kristoff
IT Telecommunications and Network Services
847-491-4094   l-grill at northwestern.edu

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