JNCIA-DevOps Practice Test 19 — 15 Questions

Question 1

A network automation script is reading a YAML configuration file containing Junos device credentials. The script encounters an unhandled exception when attempting to load the file using PyYAML. Upon inspection, the error is caused by a tab character used for indentation instead of spaces. Which YAML specification rule does this violate?

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

Accepted Answer

Tab characters are strictly forbidden for indentation in YAML.. YAML 1.2 specifications explicitly prohibit the use of the tab character for indentation. All indentation whitespace must consist exclusively of space characters to maintain hierarchy definition.

Answer

Comments must start with a double forward slash (//).

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YAML files require all keys to be wrapped in double quotes.

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Top-level keys must start with a hyphen (-) character.

Question 2

What is a primary characteristic of a DevOps culture when applied to network operations (NetOps)?

Accepted Answer

Emphasizing collaboration, automation, continuous testing, and shared responsibility between network and development teams.. NetOps applies DevOps principles like collaboration, automation, and CI/CD to network engineering.

Answer

Siloing network operations strictly away from software development teams.

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Eliminating all documentation in favor of verbal communication.

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Relying entirely on manual change approval boards for every minor configuration change.

Question 3

When retrieving configuration data in JSON format from the Junos REST API, how are Junos hierarchical container statements represented in the JSON payload structure?

Accepted Answer

As nested JSON objects reflecting the hierarchical tree structure of the CLI configuration.. Junos configuration hierarchies are translated into nested JSON objects where each container level corresponds to a JSON key whose value is an object or an array of objects.

Answer

As comma-separated string lists inside a single root array.

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As flat key-value pairs separated by dots (e.g., 'system.host-name').

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As binary encoded ASN.1 objects.

Question 4

Which TWO of the following are valid scalar values in a YAML document? (Choose two)

Accepted Answer

Integer. In YAML, a scalar is a single, indivisible value rather than a collection, so option B (Integer) is correct because values such as 42 or -7 are scalar types. Option D (String) is also correct because text values like "hello" or 'world' are scalars, whether quoted or plain. By contrast, option A (Mapping) is a collection of key-value pairs, option C (Sequence) is an ordered list of items, and option E (Block) refers to a block-style presentation of collections or scalars, not a scalar value itself, so none of those are valid scalar values.

Answer

Mapping

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Sequence

Answer

Block

Question 5

Which TWO benefits are gained by using the Junos REST API instead of traditional CLI screen-scraping in automation workflows? (Choose two)

Accepted Answer

Structured data formats (JSON or XML) eliminate the need for complex regular expression parsing of CLI text.. Option B is correct because the Junos REST API returns responses in structured formats such as JSON or XML, so automation code can parse fields directly instead of relying on fragile regular expressions to extract values from human-oriented CLI text. Option E is correct because REST API calls return standard HTTP status codes (for example 200 for success, 400 for a bad request, 401 for authentication failure) plus structured error payloads, giving automation workflows explicit, programmatic error handling that screen-scraping cannot provide. Option A is incorrect because screen-scraping typically consumes more routing-engine CPU and is less efficient than the REST API, not less. Option C is incorrect because screen-scraping is generally slower and more brittle for bulk configuration pushes than the REST API. Option D is incorrect because the Junos REST API still requires authentication configuration, such as user credentials or an access token, on the device.

Answer

CLI screen-scraping uses less CPU on the Junos routing engine than REST API.

Answer

Screen-scraping is faster than REST API for bulk configuration pushes.

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REST API requires no authentication configuration on the device.

Question 6

You have captured a baseline snapshot using JSNAPy and want to compare a newly taken snapshot against that baseline. Which JSNAPy command-line action executes this comparison?

Accepted Answer

jsnapy --check. JSNAPy's --check action compares a freshly captured snapshot against the stored baseline snapshot and reports any differences. It is the standard command for post-change verification, typically run after a configuration commit to detect drift from the known-good baseline. The --snap action captures the snapshot, while --check performs the comparison.

Answer

jsnapy --test

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jsnapy --verify

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jsnapy --compare

Question 7

An automation developer is writing a script to modify candidate configuration data on a Junos device using the REST API. Which HTTP method and request body format should be used to replace an existing configuration hierarchy?

Accepted Answer

PUT method with a JSON or XML payload representing the configuration node. The Junos REST API uses standard HTTP methods mapped to NETCONF-like operations: PUT replaces an existing configuration hierarchy at the specified URL with the payload provided (JSON or XML). To replace a configuration node, you send a PUT to the configuration endpoint with the new hierarchy in the body. POST is used to create/merge, DELETE to remove, and GET to retrieve.

Answer

POST method with form-urlencoded data

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DELETE method with an empty body

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GET method with URL parameters

Question 8

What is the primary templating engine used alongside Python for generating structured Junos configuration text in network automation workflows?

Accepted Answer

Jinja2. Jinja2 is the de facto templating engine used with Python for generating Junos configuration text in network automation. It is bundled or easily installed alongside Python, integrates natively with Ansible, and supports loops, conditionals, and variable substitution that map cleanly to Junos configuration hierarchies. Its syntax ({{ }} for variables, {% %} for logic) is widely used in Junos automation examples and Juniper's own tooling.

Answer

Ansible Engine

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Mako

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ERB

Question 9

An automation developer is examining a JSON response payload returned by a Juniper device via a REST API call. Which valid JSON data type is used to represent an ordered list of values enclosed within square brackets?

Accepted Answer

Array. In JSON, an array is an ordered list of values enclosed in square brackets. It can contain multiple values of any data type, including strings, numbers, objects, and other arrays.

Answer

String

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Object

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Boolean

Question 10

Which file extension is conventionally used for YAML data serialization files?

Accepted Answer

.yaml. YAML files conventionally use the .yaml or .yml extension. YAML (YAML Ain't Markup Language) is a human-readable data serialization standard often used for configuration files and in DevOps tools like Ansible, Kubernetes, and CI/CD pipelines. The .yaml extension is the most standard and widely recognized.

Answer

.json

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.ini

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.xml

Question 11

Which THREE architectural features distinguish the Junos REST API from traditional CLI screen-scraping (CLI automation via expect scripts)? (Choose three)

Accepted Answer

Resource-based URI routing that maps directly to configuration and operational models.. Option A is correct because the Junos REST API exposes resources through hierarchical URIs (for example /rest/conf or /rest/rpc) that map directly to Junos configuration hierarchies and operational RPC models, rather than requiring the client to parse human-readable CLI output. Option C is correct because the REST API natively returns and accepts structured payloads such as JSON and XML, allowing programmatic parsing without fragile text matching. Option E is correct because the REST API uses standard HTTP status codes (200 OK, 400 Bad Request, 401 Unauthorized, 500 Internal Server Error, etc.) so automation can handle errors deterministically instead of scanning CLI error strings. Option B is not correct because strict synchronous modal CLI configuration blocks are a characteristic of the CLI (edit/commit model), not of the REST API, which is stateless and request/response oriented. Option D is not correct because VT100 terminal emulation buffers are required by screen-scraping tools such as expect, whereas the REST API communicates over HTTP and needs no terminal emulation.

Answer

Strict enforcement of synchronous modal CLI configuration blocks.

Answer

Requirement for VT100 terminal emulation buffers.

Question 12

An automation engineer is writing a script that saves operational telemetry data gathered from a Junos router. The data needs to be written directly to an open file stream in JSON format. Which method from the Python 'json' module should be used?

Accepted Answer

json.dump(). json.dump() takes a Python object and writes it directly to a file-like stream object, whereas json.dumps() returns a string.

Answer

json.dumps()

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json.to_file()

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json.write()

Question 13

An automation script uses the Junos XML API to retrieve interface statistics every 5 minutes. The script uses the RPC with the filter for a specific interface. After several successful runs, the script suddenly receives an empty element. What is the most likely cause?

Accepted Answer

The interface has been renamed or deleted from the configuration.. The RPC returns data only for interfaces that exist in the configuration. If the specified interface is renamed or deleted, the filter matches no interface, and the response contains an empty element. Other causes like session timeout or unsupported filtering would produce errors or different responses. Administrative state does not cause an empty response.

Answer

The <get-interface-information> RPC does not support filtering by interface name.

Answer

The interface is administratively down, so no statistics are returned.

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The NETCONF session has timed out and needs to be re-established.

Question 14

Which TWO statements are true regarding NETCONF locking mechanisms on Junos devices? (Choose two)

Accepted Answer

If a NETCONF session terminates unexpectedly, any locks held by that session are automatically released by the device.. Option A is correct because Junos ties NETCONF locks to the session that acquired them; if the session drops or terminates abnormally, the device automatically releases those locks so the configuration is not left permanently locked. Option C is correct because locking the candidate datastore grants exclusive write access, blocking other users or automation scripts from committing conflicting changes until the lock is released. Option B is incorrect because the candidate datastore lock is exclusive, so only one session can hold it at a time. Option D is incorrect because locks are released through normal NETCONF operations such as or session termination, not by rebooting the Routing Engine. Option E is incorrect because locking is not required for read-only requests; it is used to protect configuration changes.

Answer

Multiple concurrent NETCONF sessions can obtain exclusive write locks on the candidate datastore at the same time.

Answer

Locks can only be released by rebooting the Routing Engine.

Answer

Locking is strictly mandatory for every single <get-config> request.

Question 15

Which THREE exceptions can be raised by PyEZ during script execution when interacting with a Junos device? (Choose three)

Accepted Answer

RpcError. PyEZ raises RpcError (option A) when an RPC sent to the Junos device returns an error response, such as a failed <rpc-error> element from the NETCONF/RPC layer. ConfigError (option C) is raised when a configuration load, commit, or related config operation fails on the device. ConnectError (option D) is raised when PyEZ cannot establish or maintain the connection to the Junos device, for example due to authentication or transport failures. DatabaseLockedError (option B) and TemplateRenderError (option E) are not PyEZ exceptions: DatabaseLockedError is not a standard PyEZ exception class, and TemplateRenderError belongs to Jinja2 templating, not PyEZ's exception hierarchy.

Answer

DatabaseLockedError

Answer

TemplateRenderError