CCNP Infrastructure Practice Question
A network engineer is deploying a new branch office that must use dynamic ARP inspection (DAI) on its access switches. The engineer wants to minimize manual configuration while ensuring that only valid IP-to-MAC bindings are permitted. Which feature should be enabled on the switches to provide the required binding information to DAI?
⚠ Common exam trap
The trap here is assuming that IP Source Guard or port security can supply the binding table that DAI needs, when in fact DHCP snooping is the feature that builds and maintains those bindings.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
DHCP snooping
Dynamic ARP inspection relies on the DHCP snooping binding table to validate ARP packets on untrusted ports. Without a source of legitimate IP-to-MAC bindings, DAI cannot distinguish spoofed ARP replies from valid ones. Enabling DHCP snooping on the access switches automatically populates that table as clients obtain leases, which satisfies the requirement to minimize manual configuration while protecting the branch office from ARP poisoning.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
802.1X
Why it's wrong here
802.1X provides port-based network access control by authenticating supplicants before granting access. It does not generate IP-to-MAC bindings for ARP inspection. Although 802.1X can be part of a secure access design, it does not fulfill the specific need to supply DAI with valid bindings, so it would not meet the stated requirement.
- ✗
IP Source Guard
Why it's wrong here
IP Source Guard filters IP traffic based on the DHCP snooping binding table, but it does not supply binding information to DAI. In this scenario, DAI needs a source of valid IP-to-MAC mappings; IP Source Guard is a consumer of that data, not a provider. Enabling it alone would not satisfy the requirement to feed DAI with trusted bindings.
- ✓
DHCP snooping
Why this is correct
DHCP snooping builds a binding table of IP address, MAC address, VLAN, and interface by snooping DHCP conversations. Dynamic ARP inspection uses this table to validate ARP packets on untrusted ports. Enabling DHCP snooping on the access switches provides the required bindings automatically, minimizing manual configuration while allowing DAI to block ARP spoofing.
- ✗
Port security
Why it's wrong here
Port security restricts the number of MAC addresses allowed on a switchport and can take action when a violation occurs. It does not create an IP-to-MAC binding table that DAI can reference. While it can help against MAC flooding, it does not provide the dynamic binding information that DAI requires to validate ARP packets in this branch office scenario.
Visual reference
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.