The answer is to configure a static ARP inspection entry or an ARP ACL for the printer. This is correct because Dynamic ARP Inspection (DAI) validates ARP packets against the DHCP snooping binding database, and since a static IP device never receives a DHCP lease, it has no entry in that database, causing its legitimate ARP packets to be dropped as invalid. On the CCNA 200-301 v2 exam, this scenario tests your understanding of DAI’s dependency on trusted bindings and the need for an alternative validation method for static hosts. A common trap is to assume that disabling DAI or adding a static MAC address alone will fix the issue, but the correct fix must explicitly authorize the static IP-MAC pair. Remember the memory tip: “Static IP? DAI needs a static ACL—no DHCP, no trust, so you must adjust.”
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: dynamic ARP Inspection (DAI) validates ARP packets by comparing them against trusted IP-to-MAC bindings to prevent ARP spoofing attacks.. 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.
A switch has DHCP snooping enabled and Dynamic ARP Inspection enabled on VLAN 30. A printer with a static IP on VLAN 30 cannot communicate because its ARP packets are being dropped.
What is the best fix?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure a static ARP inspection entry or ARP ACL for the printer.
DAI relies on trusted bindings. Static-IP devices that are not learned through DHCP often require a static ARPACL or equivalent trusted binding mechanism.
Key principle: Dynamic ARP Inspection (DAI) validates ARP packets by comparing them against trusted IP-to-MAC bindings to prevent ARP spoofing attacks.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Disable DAI on all VLANs globally.
Why it's wrong here
That is broader than necessary and weakens security unnecessarily.
When this WOULD be correct
In a scenario where a network administrator is troubleshooting a network-wide ARP spoofing issue and determines that DAI is overly restrictive across all VLANs, they may decide to disable DAI globally to restore normal ARP functionality for all devices, including printers.
✓
Configure a static ARP inspection entry or ARP ACL for the printer.
Why this is correct
Correct. Static devices need a trusted binding source.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Dynamic ARP Inspection (DAI) validates ARP packets by comparing them against trusted IP-to-MAC bindings to prevent ARP spoofing attacks.
✗
Trust the user-facing printer access port for DHCP snooping and DAI.
Why it's wrong here
Trusting an access port is usually too permissive.
When this WOULD be correct
In a scenario where a network is configured with multiple VLANs and DAI is enabled, but a specific port for a trusted device (like a server) needs to bypass DAI for legitimate traffic, trusting that port would be the correct answer. This would allow ARP packets from that trusted device to pass through without being inspected.
✗
Change the printer to use a larger MTU.
Why it's wrong here
MTU has nothing to do with DAI dropping ARP packets.
When this WOULD be correct
In a different scenario where a network is experiencing fragmentation issues due to mismatched MTU settings, a question could ask for a solution to improve communication between devices. In that case, suggesting a larger MTU for the printer could be the correct answer to resolve packet fragmentation.
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 a static ARP inspection entry or ARP ACL for the printer.Correct answer▾
Why this is correct
Correct. Static devices need a trusted binding source.
✗Disable DAI on all VLANs globally.Wrong answer — click to see why▾
Why this is wrong here
Disabling DAI globally removes ARP inspection from all VLANs, which is an overly broad solution that weakens security across the entire switch, not just for the printer's VLAN.
★ When this WOULD be the correct answer
In a scenario where a network administrator is troubleshooting a network-wide ARP spoofing issue and determines that DAI is overly restrictive across all VLANs, they may decide to disable DAI globally to restore normal ARP functionality for all devices, including printers.
Why candidates choose this
A student might think disabling DAI is a quick fix to stop ARP drops, but they overlook that DAI is a valuable security feature that should be selectively bypassed for static devices rather than disabled entirely.
✗Trust the user-facing printer access port for DHCP snooping and DAI.Wrong answer — click to see why▾
Why this is wrong here
Trusting the user-facing access port for DHCP snooping and DAI would allow all ARP traffic from that port to bypass inspection, which is too permissive and could permit ARP spoofing attacks from that port.
★ When this WOULD be the correct answer
In a scenario where a network is configured with multiple VLANs and DAI is enabled, but a specific port for a trusted device (like a server) needs to bypass DAI for legitimate traffic, trusting that port would be the correct answer. This would allow ARP packets from that trusted device to pass through without being inspected.
Why candidates choose this
A student might confuse 'trusting' a port with allowing a static device to communicate, but trust is typically applied to uplink ports (e.g., to routers or other switches), not to access ports where end devices connect.
✗Change the printer to use a larger MTU.Wrong answer — click to see why▾
Why this is wrong here
MTU (Maximum Transmission Unit) affects the size of data packets, not ARP packets. ARP packets are small and always fit within standard MTU, so changing MTU has no effect on DAI dropping ARP packets.
★ When this WOULD be the correct answer
In a different scenario where a network is experiencing fragmentation issues due to mismatched MTU settings, a question could ask for a solution to improve communication between devices. In that case, suggesting a larger MTU for the printer could be the correct answer to resolve packet fragmentation.
Why candidates choose this
A student might think that increasing MTU could help if packets are being dropped, but they confuse DAI's ARP validation with MTU-related fragmentation issues, which are unrelated.
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 common exam trap is to disable Dynamic ARP Inspection entirely or trust the user-facing access port to fix ARP packet drops from static IP devices. Disabling DAI weakens the network’s ARP spoofing protection, which is against best practices and exam expectations. Trusting access ports is too broad and can allow malicious ARP traffic, defeating the purpose of DAI. The trap is that these options seem easier but compromise security, whereas the correct approach is to configure static ARP inspection entries or ARP ACLs for static IP devices to maintain security and functionality.
Detailed technical explanation
How to think about this question
Dynamic ARP Inspection (DAI) is a security feature that validates ARP packets in a network to prevent ARP spoofing attacks. It works by intercepting all ARP requests and responses on untrusted ports and verifying them against a trusted database of IP-to-MAC bindings, typically learned via DHCP snooping. If an ARP packet does not match the trusted binding, DAI drops the packet to protect the network from malicious ARP traffic.
In environments where devices use static IP addresses, such as printers or servers, DHCP snooping does not learn their IP-to-MAC bindings. Because DAI relies on this trusted binding database, ARP packets from static IP devices are often dropped unless a static ARP inspection entry or ARP ACL is configured. This configuration explicitly tells the switch to trust ARP packets from those static devices, allowing them to communicate normally without compromising security.
A common exam trap is to disable DAI globally or trust user-facing ports to fix communication issues with static IP devices. Disabling DAI weakens network security, and trusting access ports is too permissive, potentially allowing spoofed ARP packets. The practical approach is to configure static ARP entries or ARP ACLs for static IP devices, maintaining security while ensuring proper communication. This method aligns with Cisco best practices and the CCNA exam focus on secure network design.
KKey Concepts to Remember
Dynamic ARP Inspection (DAI) validates ARP packets by comparing them against trusted IP-to-MAC bindings to prevent ARP spoofing attacks.
DHCP snooping builds the trusted binding database by learning IP-to-MAC mappings dynamically from DHCP clients on untrusted ports.
Static IP devices do not generate DHCP bindings, so their ARP packets are dropped by DAI unless static ARP entries or ARP ACLs are configured.
Configuring static ARP inspection entries or ARP ACLs allows DAI to trust ARP packets from static IP devices, enabling their communication.
Disabling DAI globally reduces network security and is not recommended as a solution for static IP device communication issues.
Trusting user-facing access ports for DHCP snooping and DAI is overly permissive and can expose the network to ARP spoofing risks.
DAI drops ARP packets that do not match trusted bindings, which can cause connectivity problems for devices with static IP addresses.
Proper DAI configuration balances security and functionality by selectively trusting static devices through static ARP entries or ACLs.
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
Dynamic ARP Inspection (DAI) validates ARP packets by comparing them against trusted IP-to-MAC bindings to prevent ARP spoofing attacks.
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 dynamic ARP Inspection (DAI) validates ARP packets by comparing them against trusted IP-to-MAC bindings to prevent ARP spoofing attacks., 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 — Dynamic ARP Inspection (DAI) validates ARP packets by comparing them against trusted IP-to-MAC bindings to prevent ARP spoofing attacks..
What is the correct answer to this question?
The correct answer is: Configure a static ARP inspection entry or ARP ACL for the printer. — DAI relies on trusted bindings. Static-IP devices that are not learned through DHCP often require a static ARP ACL or equivalent trusted binding mechanism.
What should I do if I get this 200-301 question wrong?
Review dynamic ARP Inspection (DAI) validates ARP packets by comparing them against trusted IP-to-MAC bindings to prevent ARP spoofing attacks., then practise related 200-301 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Dynamic ARP Inspection (DAI) validates ARP packets by comparing them against trusted IP-to-MAC bindings to prevent ARP spoofing attacks.
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