07-23-2009, 03:47 PM
I believe this depends on what value you are trying to determine.
If you are trying to determine the root port for a non-route bridge/switch, you add the costs associated with the outgoing interfaces on the way to the root bridge/switch.
If you are trying to determine the cost of a hello packet onto a LAN, you start at the root bridge/switch and add the port costs of the incoming interfaces on the switches/bridges, until you reach the LAN segment in question.
Correct me if I'm wrong or have misunderstood your question.
If you are trying to determine the root port for a non-route bridge/switch, you add the costs associated with the outgoing interfaces on the way to the root bridge/switch.
If you are trying to determine the cost of a hello packet onto a LAN, you start at the root bridge/switch and add the port costs of the incoming interfaces on the switches/bridges, until you reach the LAN segment in question.
Correct me if I'm wrong or have misunderstood your question.