JNCIA-DevOps Practice Exam 3 — 20 Questions

Question 1

A network automation engineer is writing a Python script using the Junos PyEZ library to retrieve operational state from a QFX Series switch. The script needs to retrieve interface statistics using an RPC instead of raw CLI text parsing. Which PyEZ method should the engineer execute to invoke the 'get-interface-information' RPC and receive the structured XML response?

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

Accepted Answer

dev.rpc.get_interface_information(). In Junos PyEZ, the dev.rpc() method is used to execute native Junos XML RPCs directly against the device and return the results as an ElementTree XML object.

Answer

dev.get_config(format='xml')

Answer

dev.load(action='set', format='xml')

Answer

dev.execute_cli('show interfaces')

Question 2

A network automation engineer is using a Python script with the PyYAML library to load a YAML file that defines a Junos device's configuration. The script needs to ensure that the loaded data is a Python dictionary and that no arbitrary Python objects are instantiated during parsing. Which function should the engineer use to safely load the YAML content?

Accepted Answer

yaml.safe_load(stream). Using yaml.safe_load ensures that only standard Python data types are constructed from the YAML input. It prevents the instantiation of arbitrary objects and mitigates security risks such as code execution. This is the recommended approach for parsing configuration files in automation scripts.

Answer

yaml.load(stream, Loader=yaml.FullLoader)

Answer

yaml.load(stream, Loader=yaml.BaseLoader)

Answer

yaml.load(stream, Loader=yaml.UnsafeLoader)

Question 3

You are writing a Python script using PyEZ to retrieve and process operational data from a Junos device. Which TWO statements correctly describe the use of PyEZ Table and View for parsing operational data? (Choose two.)

Accepted Answer

A View defines how to extract specific fields from the XML response of an RPC.. A View defines the extraction of fields from XML, and a Table uses that View to parse RPC output into a list of dictionaries. The other statements are incorrect: Tables do not auto-convert to JSON, Views can be in Python, and Tables are for operational data.

Answer

Views must be defined in a separate YAML file and cannot be coded in Python.

Answer

Tables automatically convert all XML responses into JSON format.

Answer

Tables can only retrieve configuration data, not operational data.

Question 4

An automation engineer writes a Python script that reads a Junos configuration file serialized in JSON. The file opens successfully, but parsing fails with a JSONDecodeError due to trailing commas at the end of object lists. How does standard JSON handle trailing commas compared to YAML?

Accepted Answer

JSON strictly forbids trailing commas, whereas YAML permits them in collections.. Standard JSON strictly prohibits trailing commas in objects and arrays, whereas YAML is much more lenient and allows trailing commas in sequences and mappings.

Answer

Both formats handle trailing commas identically by ignoring them.

Answer

JSON allows trailing commas, but YAML strictly forbids them.

Answer

Both JSON and YAML strictly require trailing commas for every key.

Question 5

Which THREE tasks are typical responsibilities of a network DevOps engineer managing a Junos infrastructure? (Choose three)

Accepted Answer

Writing and maintaining Python automation scripts and Jinja2 templates. Option B is correct because a network DevOps engineer on Junos infrastructure typically writes Python automation scripts using libraries such as PyEZ and ncclient, and generates configuration from Jinja2 templates to push via NETCONF or Junos CLI, which is core to infrastructure-as-code. Option C is correct because managing Git repositories, branch policies, and pull request workflows is essential for version-controlling Junos configurations and enabling peer review and rollback. Option D is correct because configuring and maintaining CI/CD pipeline tools like GitLab CI or GitHub Actions automates validation, testing, and deployment of Junos configuration changes. Option A is not a DevOps responsibility since crimping CAT6 cables is a physical layer cabling task performed by cabling technicians, not automation engineers. Option E is not a DevOps responsibility because manually rebooting every switch daily is an operational anti-pattern that automation and proper monitoring would replace.

Answer

Manually crimping CAT6 Ethernet cables in the wiring closet

Answer

Manually rebooting every switch in the data center daily

Question 6

Which python module is part of the standard library that can be used to parse XML responses returned by NETCONF?

Accepted Answer

xml.etree.ElementTree. Python's built-in xml.etree.ElementTree module provides tools for parsing and navigating XML data.

Answer

netconf.parser

Answer

xml2dict

Answer

json

Question 7

A network engineer is establishing a version control workflow for network configurations using Git. Which Git command should the engineer use to stage newly created configuration template files in the local repository working directory so they are included in the next commit?

Accepted Answer

git add. The git add command stages changes in the working directory, moving them to the staging area (index) to prepare them for a commit.

Answer

git clone

Answer

git commit

Answer

git push

Question 8

A network engineer is establishing a NETCONF session with a Junos device and needs to lock the candidate configuration to prevent concurrent modifications by other administrators. Which NETCONF operation should be executed?

Accepted Answer

. The operation allows a client to lock the configuration datastore of a device to prevent unauthorized or conflicting changes during a transaction.

Answer

<lock-config><database>candidate</database></lock-config>

Answer

<get-config><source><candidate/></source><lock/></get-config>

Answer

<edit-config><target><candidate/></target><operation>lock</operation></edit-config>

Question 9

An engineer applies a configuration change using NETCONF with <edit-config> and specifies default-operation="replace" at the top level, but includes an element with operation="merge". How does Junos evaluate this?

Accepted Answer

The specific element operation ('merge') takes precedence over the transaction-level default-operation ('replace').. Per-element operation attributes override the default-operation specified at the transaction level.

Answer

The transaction fails because default-operation and element operations conflict.

Answer

The device rolls back the configuration due to ambiguous parameters.

Answer

The default-operation takes precedence, ignoring the merge attribute.

Question 10

An automation engineer is designing a Junos network automation workflow and needs to select the component of the Junos automation architecture responsible for parsing XML and JSONRPC client requests and interacting directly with the Junos kernel and daemons. Which component fulfills this role?

Accepted Answer

mgd (Management Daemon). MGD (Management Daemon) is the primary user interface handler in Junos OS. It processes CLI commands, Netconf XML requests, and JSON-RPC APIs, translating them into operations interacting with the Junos kernel and individual routing daemons via RRDS.

Answer

jails

Answer

rpd (Routing Protocol Daemon)

Answer

jsd (Junos Script Daemon)

Question 11

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?

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.

Answer

Stateful configuration drift management

Answer

Blue-green circuit provisioning

Answer

Event-driven telemetry ingestion

Question 12

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

Answer

Manual approval of physical fiber patch cables by a security guard

Question 13

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

Answer

YAML

Answer

CSV

Question 14

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()

Answer

dev.gather_facts()

Answer

dev.get_facts()

Question 15

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.

Answer

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

Answer

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

Question 16

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

Answer

set protocols rest

Answer

set management-plane api

Question 17

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.

Answer

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

Answer

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

Answer

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

Question 18

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.

Answer

The ampersand symbol (&)

Answer

The greater-than symbol (>)

Answer

The asterisk symbol (*)

Question 19

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()

Answer

dev.version

Answer

dev.os_version

Question 20

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

Answer

.jsn

Answer

.txt