200-301 · Question #1180
What is the root port in STP?
The correct answer is D. It is the port on a switch with the lowest cost to reach the root bridge.. The root port in Spanning Tree Protocol (STP) is the port on a non-root switch that provides the least-cost path to the root bridge.
Question
Options
- AIt is the port with the highest priority toward the root bridge.
- BIt is the port on the root switch that leads to the designated port on another switch.
- CIt is the port that is elected only when the root bridge has precisely one port on a single LAN
- DIt is the port on a switch with the lowest cost to reach the root bridge.
How the community answered
(38 responses)- B3% (1)
- C5% (2)
- D92% (35)
Why each option
The root port in Spanning Tree Protocol (STP) is the port on a non-root switch that provides the least-cost path to the root bridge.
The root port is selected based on the lowest path cost, not the highest priority, to the root bridge.
The root switch does not have root ports; all its ports are designated ports.
The election of a root port is not dependent on the root bridge having precisely one port on a single LAN; every non-root switch selects a root port regardless of the root bridge's port count.
Each non-root switch in an STP topology determines its root port by identifying the port that offers the lowest cumulative path cost to reach the root bridge, ensuring the most efficient forwarding path for traffic towards the root.
Concept tested: STP root port definition
Source: https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/10556-16.html#anc3
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