From: Anthony Pace (anthonypace@xxxxxxxxxxx)
Date: Thu Jun 20 2002 - 16:11:57 GMT-3
Thanx!
I get it now. Each port has a cost which is an accumualtion of the
distance to the ROOT. The lowest cost port will forward. If I want to
set a prefernce I can use the port priority as a knob to differenciate
between equal cost ports. If I want to ABSOLUTLY make sure one port
works I would set it's cost very low, thereby overiding the dynamically
calculated cost of that port.
Does that sound correct?
Anthony Pace
On Thu, 20 Jun 2002 11:47:21 -0700, "Sasa Milic" <smilic@EUnet.yu>
said:
>
> Anthony,
>
> STP uses four criteria to determine best BPDU, in the order:
>
> 1. Lower Root Bridge ID
> 2. Lower path cost to the Root
> 3. Lower sending Bridge ID
> 4. Lower sending port ID
>
> So, once root is determined, it would use lower path cost.
> If there are two paths with equal cost, and they are going
> from the same switch (say two parallel paths between switches),
> then sending port id will be used as a tie-breaker. Port id
> consist of two fields, port priority and port number from the
> switch, so basically it would first use port priority and
> then port number, in case that priorities are equal.
>
> Sasa
> CCIE 8635
>
> Anthony Pace wrote:
> >
> > I now understand the distinction between the port and portvlan for cost
> > and priority, and that a spantree priority globally applied to each
> > VLAN or the wohole switch is for the ROOT bridge election.
> >
> > Which is used in dtermining a switches "best path to the root" ?
> >
> > portcost or portprioriy? WHat is the other one for?
>
-- Anthony Pace anthonypace@fastmail.fm-- http://fastmail.fm/ - Consolidate POP email and Hotmail in one place
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