CCNA Switching and Network Access Practice Question
A switch has a root port and an alternate port for the same VLAN. Which statement best explains the operational role of the alternate port?
⚠ Common exam trap
Don't confuse STP's redundancy roles with load balancing or congestion management. Remember, alternate ports are for backup, not active traffic routing.
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
✓
It is a backup path toward the root bridge and normally does not forward while the active root path is healthy.
The alternate port acts as a backup path toward the root bridge and stays in a non-forwarding state under normal conditions. In practical terms, STP keeps it ready in case the active path fails, but it does not allow it to forward frames while the primary root path is healthy. That is how STP preserves redundancy without creating loops. This question is useful because many learners understand root ports and designated ports but do not clearly understand what the alternate role represents.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
It is a backup path toward the root bridge and normally does not forward while the active root path is healthy.
Why this is correct
In Rapid PVST+ or classic STP, an alternate port receives a superior BPDU from another switch on the same segment, providing a redundant path to the root. It remains in discarding/blocking state while the root port is healthy, and only transitions to forwarding if the root port fails, ensuring a loop-free topology while preserving redundancy.
- ✗
It always forwards traffic at the same time as the root port for load balancing.
Why it's wrong here
In a single spanning-tree instance, an alternate port is placed in the discarding (blocking) state specifically to prevent Layer 2 loops; allowing it to forward simultaneously with the root port would create a bridging loop. Load balancing over redundant links is achieved by using multiple STP instances (for example, per-VLAN spanning tree) that assign different root ports and blocking ports in different VLANs. Therefore, an alternate port never forwards at the same time as the root port in the same VLAN.
When this WOULD be correct
If the question were to ask about a network configuration that uses multiple paths for load balancing and specifies that both the root port and alternate port can forward traffic simultaneously, then option B would be correct.
- ✗
It is the port that elects the root bridge for the VLAN.
Why it's wrong here
Election of the root bridge is a switch-level decision based on the lowest bridge ID, not something a port performs. Individual ports are assigned roles like root, designated, or alternate only after the root bridge is identified. Therefore, an alternate port does not elect the root bridge; it is simply a standby port on a segment that has another path to the root.
When this WOULD be correct
If the question asked about the role of a port in the Spanning Tree Protocol (STP) during the election process, specifically focusing on how ports contribute to determining the root bridge, then this option would be correct.
- ✗
It is a special routed port used for inter-VLAN communication.
Why it's wrong here
An alternate port is a Layer 2 STP port role that operates on switchports within a VLAN, not a routed interface. Inter-VLAN routing requires a router or Layer 3 switch with SVIs or routed ports, which do not participate in spanning-tree port roles for the same purpose. Confusing a Layer 2 blocking port with a Layer 3 routed port misrepresents the functionality of both.
When this WOULD be correct
If the question were to ask about the function of a routed port in a Layer 3 switch that facilitates inter-VLAN communication, then option D would be correct. In that scenario, the routed port would be responsible for forwarding traffic between different VLANs.
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.
✓It is a backup path toward the root bridge and normally does not forward while the active root path is healthy.Correct answer▾
Why this is correct
In Rapid PVST+ or classic STP, an alternate port receives a superior BPDU from another switch on the same segment, providing a redundant path to the root. It remains in discarding/blocking state while the root port is healthy, and only transitions to forwarding if the root port fails, ensuring a loop-free topology while preserving redundancy.
✗It always forwards traffic at the same time as the root port for load balancing.Wrong answer — click to see why▾
Why this is wrong here
Option B is incorrect because an alternate port does not forward traffic while the root port is active; it serves as a backup path and only becomes active if the root port fails.
★ When this WOULD be the correct answer
If the question were to ask about a network configuration that uses multiple paths for load balancing and specifies that both the root port and alternate port can forward traffic simultaneously, then option B would be correct.
Why candidates choose this
Candidates might choose this option due to a misunderstanding of spanning tree protocols, confusing the roles of root and alternate ports with load balancing concepts commonly used in other networking scenarios.
✗It is the port that elects the root bridge for the VLAN.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because the alternate port does not participate in the election process for the root bridge; it only serves as a backup path to the root bridge once it is established.
★ When this WOULD be the correct answer
If the question asked about the role of a port in the Spanning Tree Protocol (STP) during the election process, specifically focusing on how ports contribute to determining the root bridge, then this option would be correct.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of STP roles, confusing the functions of port types and the process of root bridge election, leading them to think that alternate ports have a role in that election.
✗It is a special routed port used for inter-VLAN communication.Wrong answer — click to see why▾
Why this is wrong here
Option D is incorrect because an alternate port is not a routed port; it operates at Layer 2 and is part of the Spanning Tree Protocol, which does not involve routing functionalities for inter-VLAN communication.
★ When this WOULD be the correct answer
If the question were to ask about the function of a routed port in a Layer 3 switch that facilitates inter-VLAN communication, then option D would be correct. In that scenario, the routed port would be responsible for forwarding traffic between different VLANs.
Why candidates choose this
Candidates may find this option tempting due to a misunderstanding of port types in VLAN configurations, conflating Layer 2 switching concepts with Layer 3 routing functionalities, leading to confusion about their roles.
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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Related to this question
Learn chapter
Configuring Switch Ports for Desktops, VoIP Phones, APs, IoT, and Virtualized Hosts
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.
Key term
VLAN
A VLAN logically segments a physical network into isolated broadcast domains without requiring separate physical switches.
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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.