JNCIA-SEC Junos OS Security Objects Practice Question
You are troubleshooting an issue where TFTP file transfers are failing across an SRX device. Traffic is permitted by security policies. What is the most likely cause of this behavior?
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
✓
The TFTP ALG is disabled or missing, preventing dynamic data port opening.
TFTP relies on UDP port 69 for initial control, but dynamically negotiates a new port for data transfer. The TFTP ALG must be active to handle this port translation.
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 TCP proxy is disabled in the security zone.
Why it's wrong here
TFTP is a UDP-based protocol, not TCP proxy-dependent.
- ✓
The TFTP ALG is disabled or missing, preventing dynamic data port opening.
Why this is correct
TFTP requires an ALG to open dynamic pinholes for the data transfer phase.
- ✗
Address books are blocking high-numbered UDP ephemeral ports.
Why it's wrong here
Address books filter by IP address/subnet, not by ephemeral port numbers.
- ✗
Screen options are misinterpreting TFTP data packets as a UDP flood attack.
Why it's wrong here
While possible if thresholds are low, ALG failure is the classic root cause for TFTP transfer failures.
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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 JNCIA-SEC 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 JNCIA-SEC exam.