The answer is that the new server has a different MAC address than the sticky MAC previously learned by the switch. This is correct because port security with sticky MAC addresses dynamically binds the first device’s MAC to the running configuration, and any subsequent device with a different MAC triggers a security violation. By default, the violation mode is shutdown, which immediately places the port into errdisable state—exactly matching the scenario where a new server is connected to a port that had already learned the previous device’s MAC. On the Cisco DCCOR / CCNP Data Center Core 350-601 exam, this concept tests your understanding of how sticky MAC interacts with violation actions, often appearing as a trap where candidates overlook that sticky entries persist across reboots unless saved. A common memory tip: “Sticky learns the first, errdisable kills the worst”—once a MAC is stuck, any change means the port gets shut.
350-601 Security Practice Question
This 350-601 practice question tests your understanding of security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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
```
switch# show port-security interface ethernet 1/1
Port Security : Enabled
Port status : Secured
Violation mode : Shutdown
Maximum MAC Addresses : 1
Sticky MAC Addresses : 1
Last violation time : 00:00:15
Last violation MAC address : 000c.291a.2b3c
```
Refer to the exhibit. An administrator connects a new server to Ethernet1/1 and the port immediately goes into errdisable state. The previous device was connected to that port. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Clue: "immediately / without restart"
Why it matters: Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.
```
switch# show port-security interface ethernet 1/1
Port Security : Enabled
Port status : Secured
Violation mode : Shutdown
Maximum MAC Addresses : 1
Sticky MAC Addresses : 1
Last violation time : 00:00:15
Last violation MAC address : 000c.291a.2b3c
```
A
The new server has a different MAC address than the sticky MAC
Sticky MAC learned the previous server's MAC; new server's MAC is different, causing a violation and port shutdown.
B
The port security violation mode is set to protect
Why wrong: Protect mode drops frames but does not errdisable the port.
C
The port security maximum MAC addresses is set too high
Why wrong: A high maximum would allow more MACs; this violation is due to mismatch.
D
The port is configured as a trunk
Why wrong: Trunk configuration is not shown and would not cause this violation.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The new server has a different MAC address than the sticky MAC
The port immediately entering errdisable state upon connecting a new server indicates a port security violation. When port security is enabled with sticky MAC addresses, the switch dynamically learns and 'sticks' the MAC address of the first connected device to the running configuration. Connecting a device with a different MAC address triggers a security violation, and if the violation mode is 'shutdown' (the default), the port is placed into errdisable state. This matches the scenario where the previous device's MAC was learned as sticky, and the new server's MAC differs.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
The new server has a different MAC address than the sticky MAC
Why this is correct
Sticky MAC learned the previous server's MAC; new server's MAC is different, causing a violation and port shutdown.
Clue confirmation
The clue words "most likely", "immediately / without restart" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The port security violation mode is set to protect
Why it's wrong here
Protect mode drops frames but does not errdisable the port.
✗
The port security maximum MAC addresses is set too high
Why it's wrong here
A high maximum would allow more MACs; this violation is due to mismatch.
✗
The port is configured as a trunk
Why it's wrong here
Trunk configuration is not shown and would not cause this violation.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that any port security violation immediately causes errdisable, but the trap here is that only the 'shutdown' and 'restrict' modes can lead to errdisable (restrict does not errdisable but logs and drops), while 'protect' silently drops traffic without disabling the port.
Trap categories for this question
Command / output trap
Trunk configuration is not shown and would not cause this violation.
Detailed technical explanation
How to think about this question
Port security with sticky MAC addresses stores the learned MAC in the running configuration as a 'sticky' entry, which persists across reloads if saved. When a new device connects, the switch compares the source MAC against the secure MAC list; if it does not match and the maximum count is reached, a violation occurs. The default violation mode is 'shutdown', which errdisables the port and requires manual or automatic recovery (e.g., 'errdisable recovery cause psecure-violation'). In real-world scenarios, this is common in campus networks where ports are locked to specific devices for security compliance.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
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.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Security — This question tests Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The new server has a different MAC address than the sticky MAC — The port immediately entering errdisable state upon connecting a new server indicates a port security violation. When port security is enabled with sticky MAC addresses, the switch dynamically learns and 'sticks' the MAC address of the first connected device to the running configuration. Connecting a device with a different MAC address triggers a security violation, and if the violation mode is 'shutdown' (the default), the port is placed into errdisable state. This matches the scenario where the previous device's MAC was learned as sticky, and the new server's MAC differs.
What should I do if I get this 350-601 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely", "immediately / without restart". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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