In spanning tree there are 4 things that each switch
looks at in making STP path choice.
1. switch with lowest root BID (priority.mac address)
2. Lowest aggregate path cost from root.
3. lowest sending switch BID (priority.mac address)
4. Lowest Port ID (port#.port priority.
In your setup you have two switches. You are making
changes on the 4th item. You will never get to this
selection criteria because you will stop at the third
most likely. If each switch is the same cost from the
root, then the lowest PID will win. If everything is
default, it will be the switch with the lowest MAC
Address. The only time the 4th comes into play, is if
the two connections originate from the same switch and
go to the same destination. What you need to do is
look at the set up and go throught the following:
1. Who is the root bridge for the VLAN in question?
use "show spantree (VLAN#)
2. Pick the root ports for every switch.
3. Choose the designated port. This is done per
segment. This is the port that the vlan traffic
will be sent to to reach the root bridge.
4. Any port that is not a root port or a designated
port will go into blocking.
All decisions for root bridge, root port, and
designated port should be based on the 4 items in the
order listed above.
Hope this helps,
William Swedberg CCNP CCDP
--- "Deloso, Elmer G." <[EMAIL PROTECTED]>
wrote:
> Hi, all. I 've tried increasing the port cost to
> have spanning-tree go in
> one direction, like SwitchA would be forwarding and
> SwitchB would be
> blocking.
> But it still ends up with SwitchB as the forwarding
> switch. Am i to
> configure
> another entry somewhere? Thanks in advance.
>
> Elmer Deloso
>
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