Quick Answer
The answer is the root port. On any nonroot switch in a Spanning Tree Protocol topology, the root port is the single port that provides the lowest path cost to the root bridge, determined by analyzing the best BPDU received on the switch. This port role is fundamental because it ensures a loop-free, logical path toward the network’s root bridge, with all other ports either blocking or forwarding based on their designated or alternate roles. On the CCNA 200-301 v2 exam, this concept tests your understanding of STP port roles and the bridge ID election process; a common trap is confusing the root port with the designated port, which is the port on a segment closest to the root bridge. To remember, think: the root port is the nonroot switch’s “best ticket” back to the root—it’s the port that hears the best BPDU. A helpful mnemonic is “Root Receives,” meaning the root port is the receiver of the superior BPDU on a nonroot switch.
This 200-301 practice question tests your understanding of switching and network access. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: a non-root switch selects one root port as its lowest-cost path back to the root bridge in STP.. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which spanning-tree port role receives the best BPDU toward the root bridge on a nonroot switch?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Designated port
Why wrong: Designated ports forward away from the root for a segment.
Alternate port
Why wrong: Alternate ports are backup paths to the root.
Root port
Correct. The root port points toward the root bridge.
Disabled port
Why wrong: A disabled port does not participate in forwarding.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Root port
The root port is the port on a nonroot switch with the lowest path cost to the root bridge.
Key principle: A non-root switch selects one root port as its lowest-cost path back to the root bridge in STP.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Designated port
Why it's wrong here
Designated ports forward away from the root for a segment.
When this WOULD be correct
In a different question asking which port role on a switch forwards traffic to the root bridge while also being the only port on a segment, the designated port would be the correct answer. This scenario would highlight its role in managing traffic flow toward the root bridge.
Alternate port
Why it's wrong here
Alternate ports are backup paths to the root.
When this WOULD be correct
In a question asking which port role can transition to forwarding state if the primary root port fails, the alternate port would be the correct answer. This scenario would focus on redundancy and failover mechanisms in spanning tree protocols.
Root port
Why this is correct
Correct. The root port points toward the root bridge.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
A non-root switch selects one root port as its lowest-cost path back to the root bridge in STP.
Disabled port
Why it's wrong here
A disabled port does not participate in forwarding.
When this WOULD be correct
In a different question asking about the state of a port that is intentionally configured to not forward traffic and is administratively shut down, a Disabled port could be the correct answer, as it would be the only port state mentioned that does not participate in STP.
Option-by-option analysis
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
Why this is correct
Correct. The root port points toward the root bridge.
Why this is wrong here
The designated port is responsible for forwarding traffic to and from a network segment and does not receive the best BPDU toward the root bridge; instead, it sends BPDUs to other ports. Therefore, it cannot be the correct answer for identifying the port role that receives the best BPDU on a nonroot switch.
★ When this WOULD be the correct answer
In a different question asking which port role on a switch forwards traffic to the root bridge while also being the only port on a segment, the designated port would be the correct answer. This scenario would highlight its role in managing traffic flow toward the root bridge.
Why candidates choose this
Candidates may confuse the roles of designated and root ports, as both are involved in the spanning tree process, leading them to mistakenly select the designated port due to its active role in forwarding traffic.
Why this is wrong here
The alternate port does not receive the best BPDU toward the root bridge; instead, it serves as a backup path to the root bridge when the primary path fails. It is in a blocking state and does not forward traffic.
★ When this WOULD be the correct answer
In a question asking which port role can transition to forwarding state if the primary root port fails, the alternate port would be the correct answer. This scenario would focus on redundancy and failover mechanisms in spanning tree protocols.
Why candidates choose this
Candidates may confuse the alternate port's role in providing redundancy with its ability to receive BPDUs, leading them to mistakenly believe it is involved in the best path selection toward the root bridge.
Why this is wrong here
A Disabled port does not participate in the Spanning Tree Protocol (STP) and does not receive any BPDUs, making it incapable of receiving the best BPDU toward the root bridge.
★ When this WOULD be the correct answer
In a different question asking about the state of a port that is intentionally configured to not forward traffic and is administratively shut down, a Disabled port could be the correct answer, as it would be the only port state mentioned that does not participate in STP.
Why candidates choose this
Candidates may confuse Disabled ports with other port roles, thinking that any port state could potentially receive BPDUs, especially if they overlook the specific requirement of receiving the best BPDU.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Be careful not to confuse port roles. Remember, the root port is specifically for receiving the best BPDU toward the root bridge, not for forwarding or redundancy.
Detailed technical explanation
Spanning Tree Protocol (STP) is a Layer 2 network protocol that prevents loops in Ethernet networks by creating a loop-free logical topology. STP elects a root bridge and then determines the best path from every switch to this root bridge. Each non-root switch selects a single port, called the root port, which provides the lowest cost path back to the root bridge. This root port is the primary forwarding port toward the root and receives the best Bridge Protocol Data Units (BPDUs) from the root bridge. The root port is chosen based on the lowest path cost to the root bridge, which is calculated by summing the costs of all links between the switch and the root. This port role is critical because it forwards traffic toward the root bridge and receives superior BPDUs compared to other ports. Designated ports forward traffic away from the root on a segment, alternate ports serve as backup paths, and disabled ports do not participate in forwarding or BPDU exchange. A common exam trap is confusing the root port with the designated or alternate ports. While designated ports forward traffic away from the root and alternate ports provide backup paths, only the root port receives the best BPDU toward the root bridge on a non-root switch. Understanding this distinction is essential for correctly answering STP questions and for practical network troubleshooting and design.
Key takeaway
A non-root switch selects one root port as its lowest-cost path back to the root bridge in STP.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Review a non-root switch selects one root port as its lowest-cost path back to the root bridge in STP., then practise related 200-301 questions on the same topic to reinforce the concept.
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FAQ
Switching and Network Access — This question tests Switching and Network Access — A non-root switch selects one root port as its lowest-cost path back to the root bridge in STP..
The correct answer is: Root port — The root port is the port on a nonroot switch with the lowest path cost to the root bridge.
Review a non-root switch selects one root port as its lowest-cost path back to the root bridge in STP., then practise related 200-301 questions on the same topic to reinforce the concept.
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
A non-root switch selects one root port as its lowest-cost path back to the root bridge in STP.
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Last reviewed: May 17, 2026
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.
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