802.1q question: port cost

I can not find why it is necessary. However it's very possible the cost has be changed by mistake. I think if it happens each bridge can not compute path cost consisently, and result in differently views of path cost, then trouble will surface. Just wonder if the specification explictly state measures or guide lines to prevent that happen, or my thought is just not right.

It's not a homework. If you really have experience will willing to share.... Otherwise why bother?

thanks for pointing out the typo. Repost it

Homework again?

think of it this way: why on earth WOULD it be neccessary?

OK, if not hoemwaork, then clarify a few things-

why is the subject line "802.1q question: port cost". I don't get the question. 802.1q is the spec for vlans - there IS no port cost option involved with vlans. There is no path computation involved in that spec.

Please clarify what you are asking. Your question seems to be about spanning tree, yet you refer to 802.1q.