The answer is that frames from the unauthorized MAC are dropped and the violation is counted while the port stays up. This is correct because port security restrict mode is designed to silently discard traffic from the violating source address while still incrementing the violation counter and optionally generating a syslog or SNMP notification. Unlike shutdown mode, the interface remains operational for all other authorized devices, and unlike protect mode, the switch actively records the violation for monitoring. On the CCNA 200-301 v2 exam, this question tests your ability to distinguish between the three violation modes—protect, restrict, and shutdown—a common trap being that protect mode also drops frames but does not log the violation. A helpful memory tip is to think of restrict as “restrict and record”: it restricts the violating MAC while keeping a record of the offense.
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: port security on Cisco switches controls access by limiting the number of MAC addresses allowed on an access port to prevent unauthorized devices from connecting.. 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.
An engineer applies this command on an access interface connected to a user PC: switchport port-security violation restrict. What happens if a second unauthorized MAC address appears on the port?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Frames from the unauthorized MAC are dropped and the violation is counted while the port stays up.
With restrict mode, the switch drops frames from the violating MAC, increments the violation counter, and can generate notifications. Unlike shutdown mode, the interface stays up. Unlike protect mode, the switch records the violation.
Key principle: Port security on Cisco switches controls access by limiting the number of MAC addresses allowed on an access port to prevent unauthorized devices from connecting.
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 port immediately goes err-disabled.
Why it's wrong here
That behavior matches shutdown mode, not restrict.
When this WOULD be correct
If the question specified a command that sets the violation mode to 'shutdown' instead of 'restrict', then the correct answer would be that the port goes err-disabled upon detecting a second unauthorized MAC address. This would align with the behavior of the shutdown mode.
✓
Frames from the unauthorized MAC are dropped and the violation is counted while the port stays up.
Why this is correct
That is the defining behavior of restrict.
Related concept
Port security on Cisco switches controls access by limiting the number of MAC addresses allowed on an access port to prevent unauthorized devices from connecting.
✗
The switch forwards the traffic but logs a warning.
Why it's wrong here
Port security does not continue forwarding violating traffic.
When this WOULD be correct
If the question stated that the command used was 'switchport port-security violation protect', then this option would be correct, as it allows the switch to forward traffic from authorized MAC addresses while dropping frames from unauthorized ones without disabling the port.
✗
The port transitions to listening and learning states.
In a different scenario where the question asks about a switchport configured with 'switchport port-security violation shutdown', the port would indeed transition to err-disabled, but if it were a question about a port security feature that allows learning of new MACs, this option could be correct.
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.
✓Frames from the unauthorized MAC are dropped and the violation is counted while the port stays up.Correct answer▾
Why this is correct
That is the defining behavior of restrict.
✗The port immediately goes err-disabled.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because the command 'switchport port-security violation restrict' does not cause the port to go into an err-disabled state; instead, it drops frames from unauthorized MAC addresses while keeping the port operational.
★ When this WOULD be the correct answer
If the question specified a command that sets the violation mode to 'shutdown' instead of 'restrict', then the correct answer would be that the port goes err-disabled upon detecting a second unauthorized MAC address. This would align with the behavior of the shutdown mode.
Why candidates choose this
Candidates may choose this option due to confusion between different port-security violation modes, particularly if they recall that some modes do disable the port, leading to a misinterpretation of the command's effect.
✗The switch forwards the traffic but logs a warning.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because the command 'switchport port-security violation restrict' does not allow the switch to forward traffic from unauthorized MAC addresses; it drops those frames instead.
★ When this WOULD be the correct answer
If the question stated that the command used was 'switchport port-security violation protect', then this option would be correct, as it allows the switch to forward traffic from authorized MAC addresses while dropping frames from unauthorized ones without disabling the port.
Why candidates choose this
Candidates may choose this option because they might confuse the behavior of port security with logging features, thinking that any unauthorized access would trigger a log warning while still allowing traffic to pass.
✗The port transitions to listening and learning states.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because the command 'switchport port-security violation restrict' does not cause the port to transition to listening and learning states; instead, it drops frames from unauthorized MAC addresses while keeping the port active.
★ When this WOULD be the correct answer
In a different scenario where the question asks about a switchport configured with 'switchport port-security violation shutdown', the port would indeed transition to err-disabled, but if it were a question about a port security feature that allows learning of new MACs, this option could be correct.
Why candidates choose this
Candidates may find this option tempting because they might confuse port security behavior with Spanning Tree Protocol (STP) states, leading them to think that unauthorized MAC addresses would trigger a state change.
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: answer the scenario, not the keyword
A frequent exam trap is mistaking the restrict violation mode for shutdown mode. Many candidates incorrectly believe that a violation in restrict mode causes the port to go err-disabled immediately, but this behavior only occurs with the shutdown mode. Another common confusion is between restrict and protect modes; protect silently drops unauthorized frames without incrementing violation counters or generating alerts, whereas restrict does both. Misunderstanding these differences can lead to incorrect answers about port behavior during security violations. Remember, restrict mode blocks unauthorized MAC addresses but keeps the port active and counts violations, which is a key distinction in Cisco port security.
Detailed technical explanation
How to think about this question
Port security is a fundamental Cisco feature used to secure switch access ports by limiting the number of MAC addresses that can be learned or statically assigned on a port. This prevents unauthorized devices from connecting to the network through that port. When port security is enabled, the switch monitors incoming frames and compares their source MAC addresses against the allowed list. If a frame arrives from a MAC address that is not permitted, the switch triggers a violation event.
The violation mode configured by the command 'switchport port-security violation restrict' determines the switch's response to unauthorized MAC addresses. In restrict mode, the switch drops frames from the violating MAC address, increments the violation counter, and can send notifications such as SNMP traps or syslog messages. Importantly, the port remains operational for authorized devices, ensuring network availability. This contrasts with shutdown mode, where the port is disabled (err-disabled) upon violation, requiring manual intervention to re-enable it.
A common exam trap is confusing restrict mode with shutdown mode. While shutdown immediately disables the port on violation, restrict mode only blocks unauthorized traffic but keeps the port up. Another confusion is with protect mode, which drops unauthorized frames silently without counting violations or alerting administrators. Understanding these subtle differences is crucial for configuring port security policies that balance security needs with network uptime. Practically, restrict mode is often preferred in environments where continuous connectivity is critical but unauthorized access must be controlled.
KKey Concepts to Remember
Port security on Cisco switches controls access by limiting the number of MAC addresses allowed on an access port to prevent unauthorized devices from connecting.
The 'switchport port-security violation restrict' command configures the port to drop frames from unauthorized MAC addresses while keeping the interface operational and counting violations.
In restrict mode, the switch increments a violation counter and can generate SNMP traps or syslog messages to alert administrators of security breaches.
Unlike shutdown mode, restrict mode does not disable the port, allowing legitimate traffic from authorized MAC addresses to continue flowing.
The protect violation mode silently drops unauthorized frames without incrementing violation counters or generating alerts, differing from restrict mode behavior.
Port security violations occur when a device with a MAC address not learned or allowed on the port attempts to send traffic.
Understanding port security violation modes is critical for maintaining network availability while enforcing security policies on access layer switches.
The restrict mode balances security enforcement and network uptime by blocking unauthorized traffic but avoiding complete port shutdown.
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
Port security on Cisco switches controls access by limiting the number of MAC addresses allowed on an access port to prevent unauthorized devices from connecting.
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 port security on Cisco switches controls access by limiting the number of MAC addresses allowed on an access port to prevent unauthorized devices from connecting., then practise related 200-301 questions on the same topic to reinforce the concept.
Network Services and Security — This question tests Network Services and Security — Port security on Cisco switches controls access by limiting the number of MAC addresses allowed on an access port to prevent unauthorized devices from connecting..
What is the correct answer to this question?
The correct answer is: Frames from the unauthorized MAC are dropped and the violation is counted while the port stays up. — With restrict mode, the switch drops frames from the violating MAC, increments the violation counter, and can generate notifications. Unlike shutdown mode, the interface stays up. Unlike protect mode, the switch records the violation.
What should I do if I get this 200-301 question wrong?
Review port security on Cisco switches controls access by limiting the number of MAC addresses allowed on an access port to prevent unauthorized devices from connecting., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Port security on Cisco switches controls access by limiting the number of MAC addresses allowed on an access port to prevent unauthorized devices from connecting.
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