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hardmultiple choiceObjective-mapped

Exhibit

SW2# show spanning-tree vlan 10

Root ID    Priority    32778
           Address     0011.1111.1111
           Cost        4
           Port        1 (GigabitEthernet0/1)

Bridge ID  Priority    32778
           Address     00aa.aaaa.aaaa

SW2 receives the following STP details for VLAN 10. Based on the exhibit, which statement is correct?

Question 1hardmultiple choice
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SW2 receives the following STP details for VLAN 10. Based on the exhibit, which statement is correct?

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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

SW2 is the root bridge for VLAN 10.

The root ID shown is different from SW2's local bridge ID.

B

Best answer

Gi0/1 on SW2 is the root port.

The output states that the root is reached through Port 1, which maps to Gi0/1.

C

Distractor review

All SW2 ports in VLAN 10 must be designated ports.

A non-root switch has a root port, and some other ports may be alternate or designated depending on topology.

D

Distractor review

STP is disabled because the priorities are equal.

Equal priority does not disable STP; the MAC portion breaks the tie.

Common exam trap

Common exam trap: answer the scenario, not the keyword

A common exam trap is to incorrectly conclude that STP is disabled when bridge priorities are equal. Candidates may mistakenly believe that equal priorities cause STP to fail or not elect a root bridge. However, STP always elects a root bridge by comparing the MAC addresses as a tiebreaker when priorities match. Another trap is assuming all ports on a non-root switch must be designated ports, ignoring the existence of a root port that leads toward the root bridge. Misreading the root port can lead to incorrect answers about port roles and network topology.

Technical deep dive

How to think about this question

Spanning Tree Protocol (STP) is a Layer 2 network protocol that prevents switching loops by electing a root bridge and blocking redundant paths. Each switch in the STP topology has a unique bridge ID composed of a priority value and the switch’s MAC address. The root bridge is the switch with the lowest bridge ID, and all other switches determine their best path to this root. This path is identified by selecting a root port, which is the port with the lowest path cost to the root bridge. When a switch receives STP information, it compares the root bridge ID in the BPDU with its own bridge ID to determine if it is the root bridge. If it is not the root, the switch selects a root port that provides the best path to the root bridge. This port forwards traffic toward the root. Other ports on the switch may be designated ports or blocked ports depending on the topology and path costs. The root port is unique per switch and is critical for loop-free forwarding. A common exam trap is assuming that equal priority values disable STP or that all ports on a non-root switch must be designated ports. In reality, STP uses the MAC address portion of the bridge ID to break ties when priorities are equal, ensuring a single root bridge is elected. Additionally, non-root switches always have one root port, which is the port with the best path to the root bridge, while other ports may be designated or blocked. Understanding these distinctions is essential for correctly interpreting STP output and avoiding misconfiguration or misinterpretation during the CCNA exam.

KKey Concepts to Remember

  • STP elects the root bridge as the switch with the lowest bridge ID, which combines priority and MAC address.
  • A non-root switch selects one root port as its lowest-cost path back to the root bridge.
  • The root port on a switch forwards traffic toward the root bridge and is unique per VLAN.
  • Designated ports are selected on segments to forward traffic away from the root and prevent loops.
  • STP uses the MAC address to break ties when bridge priorities are equal, ensuring a single root bridge.
  • Ports on a non-root switch can be root ports, designated ports, or blocked ports depending on topology.
  • The root bridge does not have a root port because it is the reference point for all path calculations.
  • STP prevents loops by blocking redundant paths and forwarding only the best path toward the root.

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?

STP elects the root bridge as the switch with the lowest bridge ID, which combines priority and MAC address.

What is the correct answer to this question?

The correct answer is: Gi0/1 on SW2 is the root port. — The root bridge has the lowest bridge ID. SW1 is the root because its bridge ID is lower than SW2's local bridge ID. On a non-root switch, the port with the best path toward the root becomes the root port, so Gi0/1 is the root port here.

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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