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: switchport port-security limits the number of MAC addresses allowed on a Layer 2 access port to prevent unauthorized device connections.. 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.
What does switchport port-security primarily protect against on an access port?
Unauthorized MAC addresses appearing on the port
Correct. That is the main purpose of port security.
OSPF route flapping
Why wrong: OSPF behavior is unrelated to host-facing switch port security.
DNS spoofing across the enterprise
Why wrong: Port security does not solve network-wide DNS threats.
Wireless rogue APs on every VLAN
Why wrong: Rogue AP detection is a different security control.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Unauthorized MAC addresses appearing on the port
Port security limits which MAC addresses can use an access port, helping prevent rogue endpoint attachment and simple CAM table abuse.
Key principle: Switchport port-security limits the number of MAC addresses allowed on a Layer 2 access port to prevent unauthorized device connections.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Unauthorized MAC addresses appearing on the port
Why this is correct
Correct. That is the main purpose of port security.
Related concept
Switchport port-security limits the number of MAC addresses allowed on a Layer 2 access port to prevent unauthorized device connections.
OSPF route flapping
Why it's wrong here
OSPF behavior is unrelated to host-facing switch port security.
When this WOULD be correct
If the question were about securing routing protocols on a network, specifically asking what measures can prevent OSPF instability, then this option could be correct. For example, a question might ask about techniques to stabilize OSPF in a network with frequent topology changes.
DNS spoofing across the enterprise
Why it's wrong here
Port security does not solve network-wide DNS threats.
When this WOULD be correct
If the question were about security measures for preventing DNS attacks in a network environment, and specifically asked about methods to secure DNS services, then this option could be correct. For example, a question might ask about protecting against DNS spoofing in a scenario involving a DNS server configuration.
Wireless rogue APs on every VLAN
Why it's wrong here
Rogue AP detection is a different security control.
When this WOULD be correct
If the exam question asked about the security measures for a wireless network environment, specifically regarding how to mitigate threats from unauthorized wireless devices, then this option could be correct. For example, a question might ask about securing a network from rogue access points across multiple VLANs.
Option-by-option analysis
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.
Why this is correct
Correct. That is the main purpose of port security.
Why this is wrong here
OSPF route flapping is related to routing protocol stability and is not addressed by switchport port-security, which focuses on controlling MAC address access on switch ports.
★ When this WOULD be the correct answer
If the question were about securing routing protocols on a network, specifically asking what measures can prevent OSPF instability, then this option could be correct. For example, a question might ask about techniques to stabilize OSPF in a network with frequent topology changes.
Why candidates choose this
Candidates may confuse port-security with general network security measures, leading them to incorrectly associate it with OSPF issues, especially if they have encountered OSPF-related questions in their studies.
Why this is wrong here
DNS spoofing is a technique used to redirect traffic by providing false DNS responses, which is not related to the function of switchport port-security on access ports. Port-security specifically focuses on controlling MAC address access, not DNS traffic.
★ When this WOULD be the correct answer
If the question were about security measures for preventing DNS attacks in a network environment, and specifically asked about methods to secure DNS services, then this option could be correct. For example, a question might ask about protecting against DNS spoofing in a scenario involving a DNS server configuration.
Why candidates choose this
Candidates may confuse general network security concepts, leading them to select DNS spoofing as a plausible threat, especially if they have encountered discussions about network vulnerabilities and security measures in their studies.
Why this is wrong here
This option is wrong because switchport port-security specifically protects against unauthorized MAC addresses on access ports, not against rogue access points, which are typically associated with wireless networks.
★ When this WOULD be the correct answer
If the exam question asked about the security measures for a wireless network environment, specifically regarding how to mitigate threats from unauthorized wireless devices, then this option could be correct. For example, a question might ask about securing a network from rogue access points across multiple VLANs.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of network security concepts, conflating wired port security with wireless security issues, leading them to believe that switchport port-security could also address rogue APs.
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
A frequent exam trap is mistaking switchport port-security as a solution for routing protocol instability or enterprise-wide threats like DNS spoofing or rogue wireless access points. Candidates might incorrectly associate port-security with OSPF route flapping or wireless rogue AP detection because these are common network security concerns. However, port-security strictly limits MAC addresses on a Layer 2 access port and does not interact with Layer 3 routing protocols or wireless security controls. Misunderstanding this scope leads to selecting incorrect answers that describe unrelated network issues, so it is critical to focus on port-security’s role in controlling physical device access via MAC addresses.
Detailed technical explanation
Switchport port-security is a Layer 2 security feature on Cisco switches that restricts input to an access port by limiting and identifying MAC addresses of the devices allowed to connect. It primarily protects against unauthorized devices connecting to the network through that port by controlling which MAC addresses are permitted. This helps prevent MAC flooding attacks and unauthorized endpoint access, which can compromise network integrity and security. When port-security is enabled on an access port, the switch can be configured to allow a specific number of MAC addresses, either learned dynamically or statically assigned. If a device with an unauthorized MAC address attempts to connect, the switch can take predefined actions such as shutting down the port, restricting traffic, or generating alerts. This mechanism enforces strict control over endpoint access at the switch port level, effectively mitigating risks from rogue devices. A common exam trap is confusing port-security with protections against routing protocol issues or broader network threats like DNS spoofing or rogue wireless APs. Port-security only controls MAC address access on a physical switch port and does not influence Layer 3 routing protocols like OSPF or enterprise-wide DNS security. Understanding this scope helps avoid selecting incorrect answers related to routing or wireless threats, which are outside port-security’s function.
Key takeaway
Switchport port-security limits the number of MAC addresses allowed on a Layer 2 access port to prevent unauthorized device connections.
Real-world example
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Review switchport port-security limits the number of MAC addresses allowed on a Layer 2 access port to prevent unauthorized device connections., then practise related 200-301 questions on the same topic to reinforce the concept.
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FAQ
Network Services and Security — This question tests Network Services and Security — Switchport port-security limits the number of MAC addresses allowed on a Layer 2 access port to prevent unauthorized device connections..
The correct answer is: Unauthorized MAC addresses appearing on the port — Port security limits which MAC addresses can use an access port, helping prevent rogue endpoint attachment and simple CAM table abuse.
Review switchport port-security limits the number of MAC addresses allowed on a Layer 2 access port to prevent unauthorized device connections., then practise related 200-301 questions on the same topic to reinforce the concept.
Switchport port-security limits the number of MAC addresses allowed on a Layer 2 access port to prevent unauthorized device connections.
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Last reviewed: May 17, 2026
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