JNCIA-DevOps Practice Test 4 — 25 Questions

Question 1

A network engineer writes a Python script using Junos PyEZ to push a configuration change. The script uses the ConfigTable or Config class. What mechanism does PyEZ use under the hood to ensure the configuration lock is released even if the script encounters an unhandled exception?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Python context managers ('with' statements) that automatically release locks and clean up session state upon exit.. Python context managers (using the 'with' statement) automatically handle acquiring and releasing locks and rolling back candidate changes on exception in PyEZ.

Answer

NETCONF keepalive timers that drop the SSH session after 1 second.

Answer

A UNIX cron job that reboots the router every 5 minutes.

Answer

Hardware watchdog timers built into the Routing Engine ASIC.

Question 2

When managing Junos configuration changes in a team environment, why is atomic configuration rollback capability crucial during automated deployments?

Accepted Answer

It ensures that either all configuration statements in a transaction are applied successfully or none are, preventing partial/corrupt states.. Atomic rollbacks ensure that if a change set fails validation or causes a network fault, the system can revert cleanly to the previous working state without partial application.

Answer

It compresses the configuration database to save NVRAM storage space.

Answer

It allows the router to dynamically rewrite Python scripts into C++ for faster execution.

Answer

It automatically backs up the entire Junos OS image to an external TFTP server.

Question 3

Which NETCONF RPC tag is used to gracefully terminate an active NETCONF session with a Junos device?

Accepted Answer

. The RPC requests graceful termination of the NETCONF session.

Answer

<terminate-session>

Answer

Answer

<kill-session>

Question 4

What is the role of the <rpc> element in a NETCONF message exchange?

Accepted Answer

It acts as a wrapper enclosing the specific NETCONF method request sent by the client to the server.. The <rpc> element is the protocol envelope used by the client to send a request to the NETCONF server.

Answer

It defines the security credentials for SSH authentication.

Answer

It stores error logs returned by the Junos routing engine.

Answer

It terminates the NETCONF session upon completion.

Question 5

What is the standard IETF RFC that defines the core NETCONF protocol architecture and operations?

Accepted Answer

RFC 6241. RFC 6241 is the definitive IETF standard defining the NETCONF Configuration Protocol.

Answer

RFC 8040

Answer

RFC 4253

Answer

RFC 7950

Question 6

You are writing a script that uses PyEZ to load a partial configuration merge. By default, what configuration database mode does the Config utility lock and load into?

Accepted Answer

The candidate configuration database. By default, PyEZ loads configuration changes into the candidate configuration database.

Answer

The rescue configuration database

Answer

A private configuration database instance

Answer

The global active configuration database

Question 7

In JSNAPy, what file format is used to define test cases and expected operational states?

Accepted Answer

YAML. JSNAPy uses YAML configuration files for defining tests and expected values.

Answer

INI

Answer

XML

Answer

JSON

Question 8

When serializing Python data structures to JSON for Junos automation payloads, which THREE parameters can be passed to json.dumps() to control formatting and readability? (Choose three)

Accepted Answer

separators. Option B, separators, is correct because json.dumps() accepts a (item_separator, key_separator) tuple that controls the characters placed between JSON elements, letting you produce compact output such as (',', ':') for smaller Junos payloads. Option C, sort_keys, is correct because setting sort_keys=True makes json.dumps() emit object keys in sorted order, which yields deterministic, diff-friendly JSON for configuration and automation scripts. Option E, indent, is correct because passing indent (for example indent=2 or indent=4) pretty-prints the JSON with newlines and that many spaces per level, improving readability of Junos payloads. Option A, max_depth, is not a valid json.dumps() parameter; Python's json module has no depth-limiting argument. Option D, strict_mode, is also not a json.dumps() parameter; the closest real argument is strict, which controls whether control characters inside strings are allowed, but 'strict_mode' itself does not exist.

Answer

max_depth

Answer

strict_mode

Question 9

During script development, an engineer encounters a YAML file containing comments and multiple configuration documents separated by document markers. Which characters are used to denote the start of a new document within a single YAML file stream?

Accepted Answer

---. In YAML, three dashes (---) indicate the start of a document, while three dots (...) indicate the end of a document.

Answer

===

Answer

...

Answer

###

Question 10

In a Junos NETCONF automation workflow, what happens during a lock operation on the configuration database? (Choose two)

Accepted Answer

Exclusive write access is acquired for the requesting session, preventing concurrent configuration modifications by other users or scripts.. Option A is correct because a Junos operation on the candidate configuration grants the requesting NETCONF session exclusive write access, so other users, CLI sessions, or automation scripts cannot modify the configuration concurrently until the lock is released. Option C is correct because the lock is held by that session and must be explicitly released with an operation, or implicitly released when the NETCONF session closes, before other processes can edit the configuration. The unmarked options are incorrect: B is false because locking the configuration database has nothing to do with powering down a Routing Engine, D is false because operational commands like 'show route' remain available and are not disabled by a configuration lock, and E is false because no firewall filters are deleted by a lock operation.

Answer

The physical routing engine is immediately powered down to prevent hardware wear.

Answer

All operational state monitoring (such as 'show route') is permanently disabled.

Answer

All firewall filters on all interfaces are automatically deleted.

Question 11

Which TWO tools or platforms are commonly used for version control and hosting of Junos automation code repositories? (Choose two)

Accepted Answer

GitHub. GitHub (C) is correct because it is a widely used web-based platform built on Git that provides repository hosting, branching, pull requests, and CI/CD integration for storing and collaborating on Junos automation code such as Python scripts, Jinja2 templates, and YAML playbooks. GitLab (E) is also correct because it is a Git-based DevOps platform offering self-managed or SaaS repository hosting, merge requests, and built-in CI/CD pipelines commonly used to manage and deploy Junos automation content. The remaining options do not belong: Adobe Photoshop (A) is an image-editing application, Microsoft Word (B) is a document word processor, and VLC Media Player (D) is a multimedia player — none of these provide Git-based version control or code repository hosting.

Answer

Adobe Photoshop

Answer

Microsoft Word

Answer

VLC Media Player

Question 12

An automation engineer is writing a Python script that retrieves the operational status of all interfaces from a Junos device using the Junos REST API. The script sends a GET request to https://device/rest/interface. The device returns an HTTP 200 OK response, but the response body is empty. The engineer examines the request and confirms that the URL is correct and the device is reachable. Which action should the engineer take to retrieve the interface status information?

Accepted Answer

Use the correct RPC endpoint, such as /rest/rpc/get-interface-information, to retrieve operational data.. The Junos REST API provides access to operational data through RPCs, not through arbitrary REST endpoints. To retrieve interface status, the correct endpoint is /rest/rpc/get-interface-information. A GET request to /rest/interface does not correspond to a valid RPC and returns an empty body. Using the proper RPC endpoint ensures the desired operational information is returned in the response.

Answer

Add the Accept: application/json header to the request.

Answer

Change the HTTP method to POST and include a JSON payload specifying the interface names.

Answer

Append the query parameter ?type=operational to the URL.

Question 13

When using Jinja2 templates in Python to generate configurations, how can you load a template file from disk prior to rendering it with variables?

Accepted Answer

Template(open('template.j2').read()). The Jinja2 `Template` class accepts a template source string, so reading the file contents with `open('template.j2').read()` and passing that string to `Template()` is a valid way to load a template from disk. This is the standard minimal pattern when you don't need Jinja2's file-system loader features. The other options reference methods or modules that do not exist in the Jinja2 API.

Answer

template.open('template.j2')

Answer

import_template('template.j2')

Answer

jinja2.load_file('template.j2')

Question 14

A network automation developer is writing a Python script that uses the Junos REST API to load a candidate configuration from a file and commit it. The developer wants to ensure the configuration is merged with the existing candidate configuration. Which HTTP method and endpoint should be used to load the configuration?

Accepted Answer

POST to /rest/conf/ with the configuration in the request body. To load configuration into the candidate configuration via the Junos REST API, an automation script sends an HTTP POST request to the /rest/conf/ endpoint with the configuration data in the request body. This operation defaults to a merge load, combining the new configuration with the existing candidate. Other methods like PUT or GET are not used for configuration loading.

Answer

GET to /rest/conf/ with the configuration as a query parameter

Answer

POST to /rest/config/ with the configuration in the request body

Answer

PUT to /rest/conf/ with the configuration in the request body

Question 15

Which PyEZ utility module should you import if you need to upgrade the Junos operating system on a remote device via a Python script?

Accepted Answer

from jnpr.junos.utils.sw import SW. The SW utility module from jnpr.junos.utils.sw is used for software installation and upgrades.

Answer

from jnpr.junos.utils.upgrade import Upgrade

Answer

from jnpr.junos.utils.config import Config

Answer

from jnpr.junos.device import OS_Update

Question 16

Which Python module is part of the standard library and provides functions to serialize and deserialize JSON data?

Accepted Answer

json. The 'json' module is part of the Python standard library and requires no external installation.

Answer

requests

Answer

yaml

Answer

junos-eznc

Question 17

Which THREE mechanisms are valid methods for authenticating and establishing a NETCONF session with a Junos device? (Choose three)

Accepted Answer

Remote RADIUS or TACACS+ AAA server integration via SSH transport. Option B is correct because NETCONF sessions are established over SSH (default TCP port 830), and the client can authenticate with a username and password just like a standard SSH login. Option C is correct because SSH public key authentication is a supported method for authenticating the NETCONF-over-SSH session, using the client's private key matched against an authorized key on the Junos device. Option A is correct because Junos can delegate authentication of NETCONF-over-SSH users to external RADIUS or TACACS+ AAA servers, so credentials are validated by the remote AAA server rather than only local accounts. Option D is wrong because NETCONF requires authenticated credentials and does not permit anonymous guest access. Option E is wrong because NETCONF uses SSH transport, not unencrypted cleartext Telnet on TCP port 23.

Answer

Anonymous guest access without credentials

Answer

Unencrypted cleartext Telnet on TCP port 23

Question 18

Which THREE features are provided by the Junos REST API daemon (jpagent) when running on a Junos device? (Choose three)

Accepted Answer

Translation between REST requests/JSON/XML payloads and Junos configuration/operational structures.. Option B is correct because jpagent's core function is to translate incoming REST requests and their JSON or XML payloads into Junos configuration and operational data structures, allowing the REST API to manipulate the same candidate/active configuration and operational command infrastructure used by the CLI. Option C is correct because jpagent manages the HTTP and HTTPS listeners, including binding to configurable ports (for example via the 'set system services rest http port' or 'https port' configuration), so clients can reach the REST endpoint. Option D is correct because jpagent performs authentication validation for REST requests against local user accounts or external AAA (RADIUS/TACACS+) before allowing access to Junos resources. Option A is incorrect because kernel-level packet forwarding and ASIC line-card optimization are handled by the Packet Forwarding Engine and related hardware/software components, not by the REST API daemon. Option E is incorrect because BGP route reflection is a routing protocol function configured under BGP, not a service provided by jpagent.

Answer

Kernel-level packet forwarding optimization for ASIC line cards.

Answer

Autonomous BGP route reflection across core routing instances.

Question 19

What is the purpose of the <hello> element exchanged immediately after establishing a NETCONF SSH session?

Accepted Answer

To exchange supported protocol capabilities and namespace identifiers.. The <hello> element is used by both client and server to exchange supported capabilities and session parameters.

Answer

To authenticate the SSH username and password.

Answer

To request an immediate reboot of the Junos routing engine.

Answer

To lock the candidate configuration database automatically.

Question 20

An automation script makes a REST API request to modify a Junos configuration. To ensure that the changes are validated and committed in a single workflow step without leaving dangling candidate changes, how can the commit parameter be handled?

Accepted Answer

Include the 'action=commit' query parameter or commit body flag with the configuration request.. The Junos REST API allows query parameters or header flags (such as '?action=commit' or dedicated commit instructions) to automatically commit changes made during a configuration modification request.

Answer

Issue an HTTP GET request to /api/configuration/commit.

Answer

Set the Transfer-Encoding header to 'commit'.

Answer

Send a separate SSH command because REST cannot commit configurations.