Question 1hardmultiple choice
Full question →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?
hardmultiple choiceObjective-mapped
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?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Distractor review
Disable DAI on all VLANs globally.
That is broader than necessary and weakens security unnecessarily.
B
Best answer
Configure a static ARP inspection entry or ARP ACL for the printer.
Correct. Static devices need a trusted binding source.
C
Distractor review
Trust the user-facing printer access port for DHCP snooping and DAI.
Trusting an access port is usually too permissive.
D
Distractor review
Change the printer to use a larger MTU.
MTU has nothing to do with DAI dropping ARP packets.
Common exam trap
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.
Technical deep dive
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.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
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?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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