CCNA Switching and Network Access Practice Question
Which spanning-tree port role receives the best BPDU toward the root bridge on a nonroot switch?
⚠ Common exam trap
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.
Answer choices
Why each option matters
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.
Answer analysis
Option-by-option breakdown
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
A designated port is the port on a LAN segment that advertises the best BPDU onto that segment, making it the forwarding port for that link. However, it is selected because it sends the strongest BPDU outward to downstream switches, not because it receives a superior BPDU toward the root. In fact, on a segment, the designated port represents the switch closest to the root but faces away from the root, so it does not receive the best BPDU toward the root—it generates it for the 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
An alternate port is a blocked port that receives a more favorable BPDU from another switch on the same segment, providing a backup path to the root that is not currently used. Because it receives a superior BPDU from a neighbor rather than from the root path itself, it is not the port that receives the best BPDU toward the root; instead, it is a port that could substitute for the root port if that path fails. Its role is to offer redundancy while being blocked, so it cannot be the correct answer.
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
The root port is the switch port with the lowest path cost to the root bridge, making it the interface that receives the best BPDU (lowest root ID, lowest cost, etc.) on a non-root switch. It is the only port role that actively forwards traffic toward the root bridge, and its selection is based on superior spanning tree information. This port is the single forwarding path to the root, which directly matches the question's requirement of receiving the best BPDU toward the root.
- ✗
Disabled port
Why it's wrong here
A disabled port is administratively shut down or has failed, meaning it is not participating in spanning tree protocol operations at all. Since it does not send or receive BPDUs, it has no role in root path selection and cannot receive the best BPDU toward the root. This port is completely inactive in the topology, making it an invalid candidate for any forwarding or receiving role, including receiving the best BPDU.
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
Why each answer is right or wrong
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.
✓Root portCorrect answer▾
Why this is correct
The root port is the switch port with the lowest path cost to the root bridge, making it the interface that receives the best BPDU (lowest root ID, lowest cost, etc.) on a non-root switch. It is the only port role that actively forwards traffic toward the root bridge, and its selection is based on superior spanning tree information. This port is the single forwarding path to the root, which directly matches the question's requirement of receiving the best BPDU toward the root.
✗Designated portWrong answer — click to see why▾
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.
✗Alternate portWrong answer — click to see why▾
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.
✗Disabled portWrong answer — click to see why▾
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?”
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Learn chapter
Configuring Switch Ports for Desktops, VoIP Phones, APs, IoT, and Virtualized Hosts
Key term
Path cost
Path cost is a numerical value assigned to each network path used by the Spanning Tree Protocol to determine the most efficient route and prevent loops in a switched network.
Key term
Switch
A switch is a networking device that connects devices on a local area network and uses MAC addresses to forward data only to the intended recipient.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.