From: Carlos G Mendioroz (tron@huapi.ba.ar)
Date: Thu Jun 03 2004 - 08:35:00 GMT-3
1: port cost is added at link destination, not at link source.
2: all ports of root bridge are forwarding by definition
(except perhaps a looped pair which is a non standard case)
because the root switch is the designated switch for all attached
segments, because it has 0 cost to the root.
There is no "secondary root" in the game, as long as the primary is up.
Root determination comes first, then root path determination (so the
secondary root may even be at the edge of the spanning tree, with no
ports in forwarding state).
Tom Young wrote:
> Hi, group
>
> I have two question about STP.
>
> 1, I set the port cost as 2000 on one switch's interface ,
> but it seems the cost couldn't be transfered to the
> downstream switch, the downstream switch still use the
> actual cost to calculate the STP. And show the
> spanning-tree on the downstream switch , I won't see the
> cost 2000 be added.
>
> 2, All the ports of root and secondary root are always
> keep forwarding status in STP calculation , even change
> the port cost to a bigger value, why ?
>
> Thanks alot
>
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-- Carlos G Mendioroz <tron@huapi.ba.ar> LW7 EQI Argentina
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