JNCIA-SEC Network Address Translation Practice Question
An administrator configures a Source NAT pool containing a single public IP address. Multiple internal users browse the web simultaneously. How does Junos OS distinguish between simultaneous sessions originating from different internal private IP addresses destined for the same external web server on port 80?
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
✓
By translating each internal source IP and ephemeral port combination into a unique source port on the single public IP address (PAT).
Junos uses Port Address Translation (PAT) by translating the different internal source IP and port combinations into unique source ports mapped to the single public pool IP address.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
By translating each internal source IP and ephemeral port combination into a unique source port on the single public IP address (PAT).
Why this is correct
PAT multiplexes multiple internal sessions onto a single public IP by assigning unique translated source ports.
- ✗
By modifying the destination port to a unique value for each internal user session.
Why it's wrong here
Destination ports (such as web port 80) are not modified for outbound source NAT; source ports are translated.
- ✗
By assigning virtual MAC addresses to each session in the ARP table.
Why it's wrong here
MAC addresses operate at Layer 2 and are not multiplexed per session for NAT.
- ✗
By queuing sessions and processing them sequentially through the single IP address.
Why it's wrong here
Sessions are processed concurrently using distinct source ports, not queued.
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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.