Quick Answer
The correct command is `set system login user guest class read-only`. This configuration works because Junos includes a predefined `read-only` login class that restricts users to viewing operational and configuration data via SSH without permitting any modifications, directly fulfilling the administrator’s requirement. On the JNCIA-Junos exam, this topic tests your understanding of Junos authentication and authorization, often appearing as a scenario where you must distinguish the `read-only` class from other predefined classes like `operator` or `super-user`. A common trap is confusing `read-only` with `operator`, which allows limited operational commands like `request`; remember that only `read-only` truly prevents all changes. For a quick memory tip, think “read-only = look, don’t touch” to recall that this class permits SSH login for viewing only, never for editing the configuration.
This JNCIA-JUNOS practice question tests your understanding of junos os fundamentals. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An administrator needs to grant a user read-only access to the device via SSH. Which configuration should be applied?
set system login user admin class operator
Why wrong: Operator class provides read-write access, not read-only.
set system login user guest class read-only
This creates a user 'guest' with read-only privileges.
set system login user readonly class super-user
Why wrong: Super-user class provides full access, not read-only.
set system login user guest class operator
Why wrong: Operator class provides read-write access.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
set system login user guest class read-only
Option B is correct because the 'read-only' class in Junos provides exactly the required level of access: users can view configuration and operational data but cannot make any changes. The 'set system login user guest class read-only' command assigns the predefined 'read-only' login class to the user 'guest', which permits SSH login with read-only privileges. This matches the administrator's requirement precisely.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
set system login user admin class operator
Why it's wrong here
Operator class provides read-write access, not read-only.
set system login user guest class read-only
Why this is correct
This creates a user 'guest' with read-only privileges.
Related concept
Read the scenario before looking for a memorised answer.
set system login user readonly class super-user
Why it's wrong here
Super-user class provides full access, not read-only.
set system login user guest class operator
Why it's wrong here
Operator class provides read-write access.
Common exam traps
The trap here is that candidates often confuse the 'operator' class with read-only access, not realizing that 'operator' permits operational mode changes (e.g., clearing logs or rebooting), whereas only the 'read-only' class truly restricts all modifications.
Detailed technical explanation
Junos login classes are defined under 'system login class' and control access via permissions flags (e.g., 'view', 'configure', 'superuser'). The predefined 'read-only' class has only the 'view' permission, which allows 'show' commands and 'show configuration' but denies any 'set', 'delete', or 'request' commands. In real-world scenarios, this is critical for auditors or monitoring tools that need to inspect device state without risk of accidental changes, and it can be further customized with 'allow-commands' or 'deny-commands' for granular control.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
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FAQ
Junos OS Fundamentals — This question tests Junos OS Fundamentals — Read the scenario before looking for a memorised answer..
The correct answer is: set system login user guest class read-only — Option B is correct because the 'read-only' class in Junos provides exactly the required level of access: users can view configuration and operational data but cannot make any changes. The 'set system login user guest class read-only' command assigns the predefined 'read-only' login class to the user 'guest', which permits SSH login with read-only privileges. This matches the administrator's requirement precisely.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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