easyMultiple Choice
CCNP Practice Question: Runs the following command on Switch SW4: SW4#…
A network engineer runs the following command on Switch SW4:
SW4# show spanning-tree vlan 40
VLAN0040 Spanning tree enabled protocol ieee Root ID Priority 24616 Address aabb.cc00.0600 Cost 8 Port 1 (GigabitEthernet0/1) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32768 (priority 32768 sys-id-ext 40) Address aabb.cc00.0700 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- ------------------------------ Gi0/1 Root FWD 8 128.1 P2p Gi0/2 Desg FWD 4 128.2 P2p Gi0/3 Desg FWD 4 128.3 P2p
Based on this output, which port is the root port?
⚠ Common exam trap
Cisco often tests the distinction between the root port (on a non-root bridge) and the designated port (on a root bridge or segment), and candidates may mistakenly think a switch with a lower-cost port is the root bridge or that all forwarding ports are root ports.
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
✓
GigabitEthernet0/1
The root port is the port on a non-root bridge that provides the lowest-cost path to the root bridge. In the output, SW4 is not the root bridge because its Bridge ID (priority 32768 + VLAN 40) is higher than the Root ID priority 24616, and the Root Cost is 8 via Gi0/1. The 'Role' column shows Gi0/1 as 'Root' and its 'Sts' is 'FWD', confirming it is the root port.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
GigabitEthernet0/1
Why this is correct
GigabitEthernet0/1 is the root port on SW4. In STP, a non-root bridge selects the single port that receives the best (lowest-cost) BPDU from the root bridge, and that port is assigned the Root role. Because the output shows Gi0/1 with role 'Root', it is the path toward the root bridge, even though SW4 itself is not the root bridge.
- ✗
GigabitEthernet0/2
Why it's wrong here
GigabitEthernet0/2 is incorrect because its role is designated ('Desg'), not root. A designated port is the port on a segment that has the best path to the root bridge and is responsible for sending BPDUs to that segment; it is not the port that receives the root bridge's superior BPDUs. Thus, Gi0/2 cannot be SW4's root port.
- ✗
GigabitEthernet0/3
Why it's wrong here
GigabitEthernet0/3 is also incorrect because its role is designated ('Desg'). Like Gi0/2, it is the forwarding port for its attached segment, but it does not receive the best BPDU from the root bridge. The root port selection is based on lowest root path cost from received BPDUs, and Gi0/1 must have a lower cost than Gi0/3, making Gi0/3 a non-root designated port.
- ✗
There is no root port because SW4 is the root bridge.
Why it's wrong here
The statement that there is no root port because SW4 is the root bridge is false. The root bridge is identified by the lowest Bridge ID (priority + MAC address), and the spanning-tree output would show SW4 as the root only if its Bridge ID matched the root ID. Since Gi0/1 has a Root role, SW4 must be a non-root switch; the root bridge has no root ports, but all non-root bridges have exactly one.
Visual reference
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-401 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 350-401 exam.