Question 1easymultiple choice
Full question →easymultiple choiceObjective-mapped
Which STP role identifies the port on a non-root switch that has the best path back to the root bridge?
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
Distractor review
Designated port
A designated port is the forwarding port for a segment, not specifically the best path on a non-root switch.
B
Best answer
Root port
That is the correct STP role.
C
Distractor review
Alternate port
An alternate port is a backup path.
D
Distractor review
Disabled port
Disabled is not the best-path role.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is mistaking the designated port for the root port. While both forward traffic, the designated port is selected per LAN segment to forward frames away from the root bridge, not necessarily providing the best path back to the root. Another trap is confusing the alternate port with the root port; alternate ports are backup paths kept in blocking state and do not forward traffic unless the root port fails. Candidates often overlook that the root port is unique per non-root switch and always represents the lowest-cost path to the root bridge, which is the key to answering this question correctly.
Technical deep dive
How to think about this question
Spanning Tree Protocol (STP) is a Layer 2 network protocol designed to prevent loops in Ethernet networks by creating a loop-free logical topology. STP elects a root bridge, which acts as the reference point for all path calculations. Each switch in the network determines the best path to the root bridge by calculating path costs based on link speeds. The port on a non-root switch that provides the lowest cost path back to the root bridge is designated as the root port. This root port is critical because it forwards frames toward the root bridge, ensuring a loop-free and efficient topology. The root port selection process involves comparing the total path cost to the root bridge through each switch port. The port with the lowest cumulative cost is chosen as the root port. If there is a tie, STP uses secondary criteria such as the sender bridge ID and port ID to break the tie. Only one root port exists per non-root switch, and it is always in the forwarding state. Other ports on the switch may be designated ports or alternate ports, which serve different roles in the STP topology. A common exam trap is confusing the root port with the designated port or alternate port roles. The designated port is the forwarding port for a LAN segment and is selected on a per-segment basis, not per switch. Alternate ports provide backup paths and remain in a blocking state unless the root port fails. Understanding these distinctions is crucial for the CCNA exam, as misidentifying the root port can lead to incorrect answers about STP behavior and network topology design.
KKey Concepts to Remember
- A non-root switch selects one root port as its lowest-cost path back to the root bridge in STP.
- The root port on a non-root switch is always in the forwarding state to send traffic toward the root bridge.
- Designated ports forward traffic away from the root bridge for a specific LAN segment and are selected per segment.
- Alternate ports provide backup paths and remain in blocking state unless the root port fails.
- STP calculates path cost based on link speed to determine the best path to the root bridge.
- Only one root port exists per non-root switch, ensuring a loop-free topology in STP.
- STP uses bridge ID and port ID as tie-breakers if multiple ports have the same path cost to the root.
- Confusing root ports with designated or alternate ports is a common exam mistake in STP questions.
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?
A non-root switch selects one root port as its lowest-cost path back to the root bridge in STP.
What is the correct answer to this question?
The correct answer is: Root port — The root port is the single port on a non-root switch that provides the lowest-cost path toward the root bridge. Designated ports forward away from the root for a segment, and alternate ports are backup paths.
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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