JNCIA-DevOps Practice Test 3 — 25 Questions

Question 1

An operations team is applying DevOps principles to network automation on Junos devices. They want to ensure that all changes to device operational states and configurations are treated as disposable and repeatable. Which DevOps practice best describes rebuilding device configurations completely from centralized version-controlled templates rather than performing manual incremental hot-patches?

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

Accepted Answer

Immutable infrastructure and declarative provisioning. Infrastructure as Code (IaC) and immutable infrastructure treat configurations as reproducible artifacts generated from source control rather than mutable, long-lived states modified ad-hoc.

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Stateful configuration drift management

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Blue-green circuit provisioning

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Event-driven telemetry ingestion

Question 2

In a CI/CD pipeline configured for Junos network changes, which THREE automated testing steps are typically performed before production deployment? (Choose three)

Accepted Answer

Static code linting of YAML data and Jinja2 templates. Option C is correct because CI/CD pipelines for Junos automation typically begin with static code linting of YAML data files and Jinja2 templates to catch syntax errors, formatting issues, and template rendering problems before any configuration is pushed. Option D is correct because a dry-run candidate configuration validation on a test Junos device or virtual instance (e.g., using 'commit check' or 'load merge' in a lab/vSRX/vMX environment) verifies that the generated configuration is syntactically and semantically accepted by Junos without affecting production. Option E is correct because automated schema validation against YANG models ensures the intended configuration data conforms to the device's data model, catching invalid leaf values, wrong types, or unsupported nodes early in the pipeline. Option A is not a testing step but a physical hardware maintenance action, and Option B is a manual human process unrelated to automated CI/CD validation, so neither belongs in an automated pre-deployment test suite.

Answer

Physical replacement of router power supply units

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Manual approval of physical fiber patch cables by a security guard

Question 3

What is the native data format returned by Junos devices when queried via REST API or NETCONF operations configured with JSON output formatting?

Accepted Answer

JSON. Junos devices natively return JSON when REST API or NETCONF operations are configured with JSON output formatting, because JSON is the structured data format the device emits for programmatic consumption. The 'accept: application/json' header or equivalent RPC attribute triggers this output.

Answer

INI

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YAML

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CSV

Question 4

You are writing a Python script to gather operational state information from a Junos device using PyEZ. Which method should you call on an open Device instance to retrieve standard hardware and OS inventory facts into a dictionary?

Accepted Answer

dev.facts. The dev.facts property on a PyEZ Device instance returns a dictionary of standard hardware and OS inventory facts, such as hostname, model, serial number, Junos version, and uptime. It is populated automatically when the Device connects and is accessed as a property, not called as a method. This is the canonical way to retrieve inventory facts in PyEZ scripts.

Answer

dev.rpc.get_system_inventory()

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dev.gather_facts()

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dev.get_facts()

Question 5

When comparing error handling between NETCONF and the Junos REST API, how are protocol-level errors communicated back to the client?

Accepted Answer

NETCONF embeds error details inside XML tags, whereas REST API uses standard HTTP status codes accompanied by structured error response bodies.. NETCONF communicates errors via XML elements embedded in the response envelope. The Junos REST API leverages standard HTTP status codes (such as 400 Bad Request, 401, 403, 404, 500) combined with detailed error payloads in the response body.

Answer

NETCONF uses HTTP status codes, while REST API uses XML <rpc-error> tags.

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NETCONF and REST API both use identical JSON error envelopes defined by RFC 7807.

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Both protocols rely exclusively on system syslog files to report errors to the client API.

Question 6

Which Junos configuration hierarchy is used to configure system services parameters related to the REST API agent?

Accepted Answer

set system services jpagent. The jpagent service is configured under the 'set system services jpagent' CLI hierarchy.

Answer

set system rest-api

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set protocols rest

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set management-plane api

Question 7

You are configuring a webhook in your version control system to trigger an automated CI/CD pipeline whenever a developer pushes a configuration commit to the main branch of your Junos automation repository. What security mechanism should be implemented on the receiving pipeline webhook endpoint?

Accepted Answer

Validating a shared secret token or HMAC cryptographic signature sent in the webhook request headers.. Webhooks should be secured using secret tokens or HMAC signatures to ensure requests genuinely originate from the trusted VCS platform.

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Opening TCP port 22 directly to the public internet without firewall rules.

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Hardcoding the developer's Linux user password inside the webhook listener script.

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Disabling all SSL/TLS certificates to allow unencrypted HTTP packet inspection.

Question 8

A Python script processes a YAML configuration template for Junos BGP neighbors. The configuration contains a multi-line banner string description. Which YAML block scalar indicator preserves newlines exactly as written in the text block?

Accepted Answer

The pipe symbol (|). The pipe symbol (|) is the YAML literal block scalar indicator, which preserves newlines and all whitespace exactly as written in the source text. This makes it the correct choice for multi-line banner strings where line breaks are semantically meaningful, such as Junos login banners or BGP neighbor descriptions.

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The ampersand symbol (&)

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The greater-than symbol (>)

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The asterisk symbol (*)

Question 9

An automation script needs to check if a Junos device supports a specific feature before executing an RPC. Which PyEZ property can be checked to inspect the software version loaded on the device?

Accepted Answer

dev.facts['version']. The PyEZ Device object exposes device facts through the `dev.facts` dictionary, and the loaded Junos software version is stored under the key `'version'`. Accessing `dev.facts['version']` returns the string reported by the device (for example, '21.4R3-S2.6'), which a script can parse to decide whether a feature RPC is supported. This is the canonical PyEZ pattern for version inspection.

Answer

dev.get_version()

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dev.version

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dev.os_version

Question 10

Which TWO of the following are valid extensions commonly used for YAML files? (Choose two)

Accepted Answer

.yaml. Option C (.yaml) is correct because .yaml is the canonical, officially recommended file extension for YAML documents, as defined by the YAML specification and used by tools like PyYAML, Kubernetes manifests, and Ansible playbooks. Option E (.yml) is also correct because .yml is the widely accepted short-form alternative extension for YAML files, supported by virtually all YAML parsers and commonly seen in CI/CD configs such as .travis.yml, docker-compose.yml, and GitHub Actions workflows. Option A (.xml) is incorrect because it denotes Extensible Markup Language files, a completely different markup syntax with angle-bracket tags, not YAML's indentation-based structure. Option B (.jsn) is incorrect because it is not a standard extension for any common serialization format; JSON files use .json, and .jsn is not a recognized YAML extension. Option D (.txt) is incorrect because plain-text files have no defined structure and are not parsed as YAML by convention, even though YAML is technically a text format.

Answer

.xml

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.jsn

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.txt

Question 11

When writing a Python script that connects to multiple Junos devices concurrently using PyEZ, which Python module is commonly used to manage thread pooling and parallel execution?

Accepted Answer

concurrent.futures. The concurrent.futures module is the standard Python library for managing thread pools and parallel execution. It provides ThreadPoolExecutor and ProcessPoolExecutor, which are commonly used with PyEZ to connect to multiple Junos devices concurrently. This is the recommended approach for parallel device operations in Python scripts.

Answer

jnpr.junos.parallel

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multiprocessing.device

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asyncio.netconf

Question 12

In a DevOps pipeline managing Junos devices, an engineer implements 'Infrastructure as Code' (IaC). Which practice best exemplifies this methodology when applied to Junos routing policies?

Accepted Answer

Defining routing policies in Jinja2 templates and YAML data files, committing them to Git, and automatically pushing them via Ansible playbooks.. IaC defines infrastructure in declarative configuration files stored in version control, allowing automated testing and deployment.

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Writing custom Python scripts that use regex to parse 'show route' outputs on the fly.

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Manually logging into each router via SSH during a maintenance window to type out policy-options statements.

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Using dynamic routing protocols like BGP to automatically advertise prefixes without human intervention.

Question 13

An engineer needs to explain the primary advantage of treating network configurations as code in a modern DevOps workflow. Which principle best describes this approach?

Accepted Answer

Storing configurations in a version control system to track history, enable rollbacks, and facilitate collaboration.. Treating network configurations as code allows infrastructure to be version-controlled, repeatedly deployed, and tested just like software code.

Answer

Immutable infrastructure deployment where devices are replaced rather than updated manually.

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Compiling the network CLI commands into binary machine code before executing them on Junos devices.

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Automating the complete removal of the command-line interface in favor of graphical topology builders.

Question 14

When writing a Python script to interact with Junos devices, you want to ensure that password credentials are not hardcoded in the source code. What is a recommended best practice supported by PyEZ?

Accepted Answer

Using SSH key-based authentication or environment variables/config files (.junodes). PyEZ natively supports configuration files like ~/.junodes or passing parameters dynamically, but also respects environment variables or SSH keys.

Answer

Disabling authentication in the script

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Storing credentials in plaintext in a public GitHub repository

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Hardcoding credentials in base64 encoding

Question 15

You send an edit-config RPC with an invalid XML tag name. What is the standard structure of the error returned in the <rpc-reply>?

Accepted Answer

An element containing diagnostic sub-elements like and .. NETCONF errors are returned inside an element containing details such as error-type, error-tag, and error-message.

Answer

A standard Linux kernel panic log string.

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An HTTP 400 Bad Request status code.

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A syslog message printed directly to the terminal emulator.

Question 16

Which TWO statements are true regarding the NETCONF protocol hello message exchange? (Choose two.)

Accepted Answer

Both client and server exchange capabilities using XML elements containing URI strings.. Option C is correct because in the NETCONF hello exchange both peers send a element containing a list, where each capability is expressed as a URI string (for example urn:ietf:params:netconf:base:1.0 or urn:ietf:params:netconf:capability:candidate:1.0), allowing each side to learn the other's supported features. Option D is correct because the server's hello includes a element, a positive integer attribute that uniquely identifies the NETCONF session for the duration of that connection. Option A is wrong because database locking is performed later with operations, not during the hello exchange, and the hello occurs before any configuration operations. Option B is wrong because the client hello advertises supported capabilities, not a list of YANG modules it intends to modify. Option E is wrong because the hello exchange is mandatory in NETCONF regardless of the SSH authentication method used.

Answer

The client uses the hello message to lock the configuration database before session initialization.

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The client hello message must include the list of YANG modules it intends to modify during the session.

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The hello message exchange is optional if a pre-shared SSH key is used for authentication.

Question 17

An automation engineer is writing a Python script that uses the ncclient library to connect to a Junos device via NETCONF. The engineer wants to retrieve the entire candidate configuration from the device. Which NETCONF operation should be used?

Accepted Answer

with source set to . To retrieve the candidate configuration via NETCONF, the correct operation is with the source datastore specified as . This operation reads configuration data from the chosen datastore. Other operations like target running state and configuration, modifies datastores, and changes configuration. Therefore, is the proper choice.

Answer

<get> with a subtree filter for configuration

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<copy-config> from running to candidate

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<edit-config> with operation 'get'

Question 18

In a Junos automation environment, what role does a schema (such as YANG or Junos XSD) play when interacting with NETCONF?

Accepted Answer

It defines the structural rules, data types, and valid hierarchy for configuration and operational data models.. YANG or XSD schemas define the data model structure, types, and constraints for configuration and operational data.

Answer

It encrypts the communication channel between the client and the Junos device.

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It acts as a firewall filter blocking unauthorized IP addresses on the management interface.

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It compiles Python scripts into executable machine code for the Routing Engine CPU.

Question 19

An automation engineer stores Junos interface descriptions in a YAML file. One description includes the text 'Link: 10G uplink to core-sw-01'. After loading the file with a standard YAML parser, the engineer finds the value is not parsed as expected. Which YAML syntax should the engineer use to store this value correctly?

Accepted Answer

Wrap the value in double quotes: "Link: 10G uplink to core-sw-01". YAML plain scalars cannot contain a colon followed by a space because that sequence signals a mapping key-value separator. Quoting the scalar with double quotes (or single quotes) tells the parser to treat the entire content as a literal string. This preserves the description exactly as intended so Junos configuration templates receive the correct value.

Answer

Prefix the value with an ampersand: &Link: 10G uplink to core-sw-01

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Enclose the value in square brackets: [Link: 10G uplink to core-sw-01]

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Escape the colon with a backslash: Link\: 10G uplink to core-sw-01

Question 20

You are writing a script that uses Jinja2 to dynamically render a Junos interface configuration. Which Python module and function are required to load a template from the local filesystem and render it with a dictionary of variables?

Accepted Answer

from jinja2 import Environment, FileSystemLoader. The standard Jinja2 API for loading templates from disk is to create an Environment with a FileSystemLoader pointed at the template directory, then call get_template() and render() with a variable dictionary. This is the canonical Python Jinja2 pattern and works directly with Junos config templates. PyEZ does not provide its own Jinja2 wrapper module for this purpose.

Answer

from jnpr.junos.cfg import ConfigTemplate

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from jnpr.junos.template import TemplateRenderer

Answer

import jnpr.junos.utils.jinja as jinja