Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
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?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Best answer
It is a backup path toward the root bridge and normally does not forward while the active root path is healthy.
This is correct because an alternate port is a standby path in STP.
B
Distractor review
It always forwards traffic at the same time as the root port for load balancing.
This is wrong because normal STP does not use the alternate port for simultaneous forwarding in that way.
C
Distractor review
It is the port that elects the root bridge for the VLAN.
This is wrong because ports do not elect the root bridge in that manner.
D
Distractor review
It is a special routed port used for inter-VLAN communication.
This is wrong because alternate is an STP Layer 2 port role, not a Layer 3 interface type.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is assuming the alternate port forwards traffic simultaneously with the root port for load balancing. This misconception arises because some technologies use multiple active paths, but STP’s alternate port is strictly a backup and remains blocked while the root port is healthy. Misunderstanding this can lead to incorrect answers suggesting the alternate port actively forwards frames or participates in root bridge election. Remember, the alternate port only forwards if the root port fails, preventing loops by blocking redundant paths under normal conditions.
Technical deep dive
How to think about this question
Spanning Tree Protocol (STP) is a Layer 2 protocol designed to prevent switching loops in Ethernet networks by selectively blocking redundant paths. Each non-root switch selects a single root port, which is the port with the lowest path cost to the root bridge. To maintain redundancy, STP also identifies alternate ports, which provide backup paths to the root bridge but remain in a blocking state to avoid loops. These alternate ports do not forward traffic unless the active root port fails. The decision process for STP port roles involves comparing path costs and bridge IDs to elect the root bridge and determine the best path to it. The root port is the primary forwarding port toward the root bridge, while the alternate port is a standby port that offers a backup path. If the root port goes down, the alternate port immediately transitions to forwarding state, ensuring minimal network disruption. This behavior preserves network stability and redundancy without causing broadcast storms or loops. A common exam trap is confusing the alternate port with a load-balancing or routing port. Unlike routing interfaces or EtherChannel links, the alternate port does not forward traffic simultaneously with the root port. It is strictly a backup path in STP and remains blocked unless needed. Practically, this means network engineers must understand that alternate ports are part of STP’s loop prevention mechanism and not involved in Layer 3 routing or load balancing, which helps avoid misconfigurations and exam mistakes.
KKey Concepts to Remember
- Spanning Tree Protocol (STP) selects one root port on a non-root switch as the lowest-cost path toward the root bridge for each VLAN.
- An alternate port in STP provides a backup path to the root bridge and remains in a blocking state to prevent Layer 2 loops.
- The alternate port does not forward traffic while the root port is active and healthy, ensuring network redundancy without loops.
- STP port roles such as root port, designated port, and alternate port are Layer 2 concepts and do not involve Layer 3 routing functions.
- The root bridge is elected based on the lowest bridge ID, and ports do not elect the root bridge themselves but participate in the election process.
- STP prevents Layer 2 loops by blocking redundant paths, with alternate ports serving as standby links ready to transition if the active path fails.
- Alternate ports differ from designated ports by not forwarding frames under normal conditions, unlike designated ports which actively forward traffic.
- Understanding the alternate port role helps avoid confusion with load balancing or routing concepts, which are unrelated to STP port roles.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
Spanning Tree Protocol (STP) selects one root port on a non-root switch as the lowest-cost path toward the root bridge for each VLAN.
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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