JNCIS-ENT Layer 2 Security Practice Question
You are troubleshooting a Dynamic ARP Inspection (DAI) deployment on an EX4300 switch. Clients on VLAN 20 are experiencing intermittent loss of connectivity. You run 'show arp inspection statistics' and notice dropped packets due to 'invalid-ip'. What is the most likely cause of these drops?
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
✓
Clients are using statically assigned IP addresses that do not exist in the DHCP snooping binding database.
DAI relies on the DHCP snooping database to validate ARP bindings. If a client uses a static IP address or if the DHCP binding has expired/not been learned, DAI drops the ARP reply/request because it cannot match the IP-to-MAC binding in the DHCP snooping database.
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 uplink port connecting to the default gateway is missing the 'set protocols arp-inspection trust' statement.
Why it's wrong here
Missing trust on the uplink causes drops categorized as invalid-mac or general interface drops, but static clients or mismatched bindings trigger invalid-ip.
- ✓
Clients are using statically assigned IP addresses that do not exist in the DHCP snooping binding database.
Why this is correct
Static IP addresses bypass DHCP, meaning no entry is created in the DHCP snooping database, causing DAI to drop their ARP packets as invalid.
- ✗
MAC limiting has tripped on the access port, causing ARP packets to be discarded.
Why it's wrong here
MAC limiting blocks traffic at the port security layer, separate from DAI inspection logic.
- ✗
The ARP inspection rate-limit has been exceeded on the access ports.
Why it's wrong here
Exceeding the rate limit results in drops categorized under rate-limit statistics, not invalid-ip.
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 |
About these practice questions
Courseiva writes every JNCIS-ENT question from scratch — 519 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official Juniper Networks exam blueprint
This JNCIS-ENT practice question is part of Courseiva's free Juniper Networks 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 JNCIS-ENT exam.