What value is primarily used to determine which port becomes the root port on each nonroot switch in a spanning-tree topology? A

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问题 What value is primarily used to determine which port becomes the root port on each nonroot switch in a spanning-tree topology?
A. path cost
B. lowest port MAC address
C. VTP revision number
D. highest port priority number
E. port priority number and MAC address
F. None of the above

选项

答案A

解析 Explanation:
At the conclusion of the root bridge election process, the switches move on to selecting Root Ports. The Root Port of a bridge is the port that is closest to the Root Bridge in terms of Path Cost.

Every non-Root Bridge must select one Root Port. Again, bridges use the concept of cost to measure closeness. As with some routing metrics, the measure of closeness using STP is not necessarily reflected by hop count. Specifically, bridges track what is referred to as Root Path Cost, which is the cumulative cost of all links to the Root Bridge.
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