CCNA Switching and Network Access Practice Question
This 200-301 practice question tests your understanding of switching and network access. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
SW1#show running-config | section vlan|spanning-tree|interface
vlan 10,20
spanning-tree mode rapid-pvst
spanning-tree vlan 10 priority 4096
spanning-tree vlan 20 priority 4096
!
interface GigabitEthernet0/1
switchport mode trunk
!
interface GigabitEthernet0/2
switchport mode access
switchport access vlan 10
!
interface GigabitEthernet0/3
switchport mode access
switchport access vlan 20
!
interface GigabitEthernet0/4
switchport mode access
switchport access vlan 10
SW1#show interfaces status | include err
Gi0/3 err-disabled auto auto 10/100/1000
SW1#show spanning-tree vlan 10
VLAN0010
Spanning tree enabled protocol rstp
Root ID Priority 4096
Address aaaa.bbbb.cccc
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 4096 (priority 4096 sys-id-ext 10)
Address aaaa.bbbb.cccc
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 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 128.2 P2p
Gi0/4 Desg FWD 4 128.4 P2p
SW1#show spanning-tree vlan 20
VLAN0020
Spanning tree enabled protocol rstp
Root ID Priority 4096
Address aaaa.bbbb.cccc
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 4096 (priority 4096 sys-id-ext 20)
Address aaaa.bbbb.cccc
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 Desg FWD 4 128.1 P2p
Gi0/3 Desg BLK 4 128.3 P2p
You are connected to switch SW1 via console. The network uses Rapid-PVST+ and you need to ensure that SW1 becomes the root bridge for VLANs 10 and 20. Additionally, configure PortFast and BPDU Guard on interface GigabitEthernet0/2, which connects to an end host. Finally, diagnose why interface GigabitEthernet0/3 is in err-disabled state and bring it back operational.
SW1#show running-config | section vlan|spanning-tree|interface
vlan 10,20
spanning-tree mode rapid-pvst
spanning-tree vlan 10 priority 4096
spanning-tree vlan 20 priority 4096
!
interface GigabitEthernet0/1
switchport mode trunk
!
interface GigabitEthernet0/2
switchport mode access
switchport access vlan 10
!
interface GigabitEthernet0/3
switchport mode access
switchport access vlan 20
!
interface GigabitEthernet0/4
switchport mode access
switchport access vlan 10
SW1#show interfaces status | include err
Gi0/3 err-disabled auto auto 10/100/1000
SW1#show spanning-tree vlan 10
VLAN0010
Spanning tree enabled protocol rstp
Root ID Priority 4096
Address aaaa.bbbb.cccc
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 4096 (priority 4096 sys-id-ext 10)
Address aaaa.bbbb.cccc
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 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 128.2 P2p
Gi0/4 Desg FWD 4 128.4 P2p
SW1#show spanning-tree vlan 20
VLAN0020
Spanning tree enabled protocol rstp
Root ID Priority 4096
Address aaaa.bbbb.cccc
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 4096 (priority 4096 sys-id-ext 20)
Address aaaa.bbbb.cccc
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 Desg FWD 4 128.1 P2p
Gi0/3 Desg BLK 4 128.3 P2p
A
Configure SW1 with spanning-tree vlan 10,20 priority 4096, enable PortFast and BPDU Guard on Gi0/2, and recover Gi0/3 by identifying the cause and using shutdown/no shutdown.
This is correct because setting the priority to 4096 ensures SW1 becomes root for VLANs 10 and 20 (lower priority wins). PortFast and BPDU Guard on Gi0/2 protect against loops from end hosts. For Gi0/3, err-disable recovery requires identifying the cause (e.g., via show interfaces) and then administratively shutting and no shutting the interface.
B
Set SW1's priority to 0 for VLANs 10 and 20, enable PortFast on Gi0/2, and recover Gi0/3 by reloading the switch.
Why wrong: This is incorrect because setting priority to 0 is not a valid configuration (priority values are multiples of 4096, and 0 is reserved). Additionally, reloading the switch is an unnecessary and disruptive recovery method; err-disable recovery should be done with shutdown/no shutdown or errdisable recovery cause commands.
C
Configure SW1 with spanning-tree vlan 10,20 root primary, enable PortFast and BPDU Guard globally, and recover Gi0/3 by using the 'errdisable recovery cause all' command.
Why wrong: This is incorrect because 'spanning-tree vlan root primary' sets priority to 24576 or lower if the current root has a lower priority, but it does not guarantee a specific priority like 4096. Enabling PortFast and BPDU Guard globally is not recommended; they should be applied per interface. The 'errdisable recovery cause all' command enables automatic recovery but does not immediately recover the interface; manual shutdown/no shutdown is needed for immediate recovery.
D
Set SW1's priority to 8192 for VLANs 10 and 20, enable PortFast on Gi0/2, and recover Gi0/3 by removing and reinserting the cable.
Why wrong: This is incorrect because priority 8192 is higher than 4096, so SW1 would not become root if another switch has a lower priority. Enabling only PortFast without BPDU Guard leaves the port vulnerable to BPDU attacks. Physically removing and reinserting the cable is not a valid recovery method; the interface must be administratively recovered.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure SW1 with spanning-tree vlan 10,20 priority 4096, enable PortFast and BPDU Guard on Gi0/2, and recover Gi0/3 by identifying the cause and using shutdown/no shutdown.
To make SW1 the root bridge for VLANs 10 and 20, configure 'spanning-tree vlan 10,20 priority 4096' (a valid multiple of 4096). Interface Gi0/2 connects to an end host, so enable PortFast with 'spanning-tree portfast' and BPDU Guard with 'spanning-tree bpduguard enable' under the interface to protect against accidental BPDU reception. Gi0/3 is in err-disabled state. Common causes include a port-security violation, UDLD misconfiguration, or a loopback detection. To recover, identify the cause with 'show interfaces status err-disabled', then administratively shut and no shut the interface. Option A correctly accomplishes these tasks. Option B uses an invalid priority value (0) and reloading the switch is unnecessary. Option C configures 'root primary', which sets priority to 24576 but not 4096, and globally enabling PortFast and BPDU Guard is not recommended; also 'errdisable recovery cause all' might recover the port automatically but does not address the root cause. Option D uses priority 8192 (too high) and physical cable manipulation is not a valid recovery method.
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Configure SW1 with spanning-tree vlan 10,20 priority 4096, enable PortFast and BPDU Guard on Gi0/2, and recover Gi0/3 by identifying the cause and using shutdown/no shutdown.
Why this is correct
This is correct because setting the priority to 4096 ensures SW1 becomes root for VLANs 10 and 20 (lower priority wins). PortFast and BPDU Guard on Gi0/2 protect against loops from end hosts. For Gi0/3, err-disable recovery requires identifying the cause (e.g., via show interfaces) and then administratively shutting and no shutting the interface.
Related concept
Access ports place end devices into a single VLAN.
✗
Set SW1's priority to 0 for VLANs 10 and 20, enable PortFast on Gi0/2, and recover Gi0/3 by reloading the switch.
Why it's wrong here
This is incorrect because setting priority to 0 is not a valid configuration (priority values are multiples of 4096, and 0 is reserved). Additionally, reloading the switch is an unnecessary and disruptive recovery method; err-disable recovery should be done with shutdown/no shutdown or errdisable recovery cause commands.
✗
Configure SW1 with spanning-tree vlan 10,20 root primary, enable PortFast and BPDU Guard globally, and recover Gi0/3 by using the 'errdisable recovery cause all' command.
Why it's wrong here
This is incorrect because 'spanning-tree vlan root primary' sets priority to 24576 or lower if the current root has a lower priority, but it does not guarantee a specific priority like 4096. Enabling PortFast and BPDU Guard globally is not recommended; they should be applied per interface. The 'errdisable recovery cause all' command enables automatic recovery but does not immediately recover the interface; manual shutdown/no shutdown is needed for immediate recovery.
✗
Set SW1's priority to 8192 for VLANs 10 and 20, enable PortFast on Gi0/2, and recover Gi0/3 by removing and reinserting the cable.
Why it's wrong here
This is incorrect because priority 8192 is higher than 4096, so SW1 would not become root if another switch has a lower priority. Enabling only PortFast without BPDU Guard leaves the port vulnerable to BPDU attacks. Physically removing and reinserting the cable is not a valid recovery method; the interface must be administratively recovered.
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.
✓Configure SW1 with spanning-tree vlan 10,20 priority 4096, enable PortFast and BPDU Guard on Gi0/2, and recover Gi0/3 by identifying the cause and using shutdown/no shutdown.Correct answer▾
Why this is correct
This is correct because setting the priority to 4096 ensures SW1 becomes root for VLANs 10 and 20 (lower priority wins). PortFast and BPDU Guard on Gi0/2 protect against loops from end hosts. For Gi0/3, err-disable recovery requires identifying the cause (e.g., via show interfaces) and then administratively shutting and no shutting the interface.
✗Set SW1's priority to 0 for VLANs 10 and 20, enable PortFast on Gi0/2, and recover Gi0/3 by reloading the switch.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error: Priority 0 is not a valid STP priority value; valid values are 0-61440 in increments of 4096, but 0 is reserved and not used in Cisco IOS. Also, reloading is not the recommended recovery for err-disable.
Why candidates choose this
Candidates might think that setting priority to 0 guarantees root bridge status, but they forget the valid range. They may also assume reloading clears all errors, but it is overkill and not best practice.
✗Configure SW1 with spanning-tree vlan 10,20 root primary, enable PortFast and BPDU Guard globally, and recover Gi0/3 by using the 'errdisable recovery cause all' command.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error: 'root primary' does not set a fixed priority; it adjusts dynamically. Global PortFast and BPDU Guard can cause issues on trunk ports. 'errdisable recovery cause all' only enables automatic recovery after a timeout, not immediate recovery.
Why candidates choose this
Candidates may think 'root primary' is a simpler way to ensure root status, but they overlook that it may not result in priority 4096. They might also assume global configuration is equivalent to per-interface, and that errdisable recovery commands immediately fix the port.
✗Set SW1's priority to 8192 for VLANs 10 and 20, enable PortFast on Gi0/2, and recover Gi0/3 by removing and reinserting the cable.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error: Priority 8192 does not guarantee root bridge status if another switch has a lower priority. BPDU Guard is required on edge ports. Cable reseating does not clear err-disable state.
Why candidates choose this
Candidates might think any low priority ensures root, but they forget that 4096 is lower than 8192. They may also think PortFast alone is sufficient for edge ports, ignoring BPDU Guard. Some might attempt physical troubleshooting instead of proper CLI recovery.
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?”
Common exam traps
Common exam trap: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Trap categories for this question
Command / output trap
This is incorrect because setting priority to 0 is not a valid configuration (priority values are multiples of 4096, and 0 is reserved). Additionally, reloading the switch is an unnecessary and disruptive recovery method; err-disable recovery should be done with shutdown/no shutdown or errdisable recovery cause commands.
Detailed technical explanation
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
Access ports place end devices into a single VLAN.
Trunk ports carry multiple VLANs between switches.
Allowed VLAN lists decide which VLANs can cross a trunk.
Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
→Use show vlan brief to verify access VLANs.
→Use show interfaces trunk to verify trunk state and allowed VLANs.
→Do not treat every same-VLAN issue as a routing problem.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Real-world example
How this comes up in practice
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-301 questions on switching, trunking, and access-port configuration.
Switching and Network Access — This question tests Switching and Network Access — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: Configure SW1 with spanning-tree vlan 10,20 priority 4096, enable PortFast and BPDU Guard on Gi0/2, and recover Gi0/3 by identifying the cause and using shutdown/no shutdown. — To make SW1 the root bridge for VLANs 10 and 20, configure 'spanning-tree vlan 10,20 priority 4096' (a valid multiple of 4096). Interface Gi0/2 connects to an end host, so enable PortFast with 'spanning-tree portfast' and BPDU Guard with 'spanning-tree bpduguard enable' under the interface to protect against accidental BPDU reception. Gi0/3 is in err-disabled state. Common causes include a port-security violation, UDLD misconfiguration, or a loopback detection. To recover, identify the cause with 'show interfaces status err-disabled', then administratively shut and no shut the interface. Option A correctly accomplishes these tasks. Option B uses an invalid priority value (0) and reloading the switch is unnecessary. Option C configures 'root primary', which sets priority to 24576 but not 4096, and globally enabling PortFast and BPDU Guard is not recommended; also 'errdisable recovery cause all' might recover the port automatically but does not address the root cause. Option D uses priority 8192 (too high) and physical cable manipulation is not a valid recovery method.
What should I do if I get this 200-301 question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-301 questions on switching, trunking, and access-port configuration.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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