STP Cost

I am having a hard time understanding STP cost and how links get chosen over
others.

Example

SW1----- SW2
  | / |
  | / |
  | / |
 SW3-----SW4

SW3 is root for VLAN 10, 20, 30, 40
SW2 is root for VLAN 50, 60.

When I set the STP cost to 5 on the trunk between SW1 and SW3 and the trunk
between SW2 and SW3 fail, the STP root ports on SW2 is the trunk from SW2 to
SW1.

I am confused as to why the cost has to be set on the link between SW1 and
SW3 to get this behavior instead of the link between SW1 and SW2.

Thanks,
Don.

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Received on Fri Oct 16 2009 - 16:15:47 ART