JNCIA-DevOps Practice Questions

Question 1

An automation engineer is reviewing data serialization formats used within Junos automation workflows. Which TWO statements are correct regarding JSON syntax and data types? (Choose two)

Accepted Answer

JSON object keys must be enclosed in double quotes.. Option C is correct because JSON (RFC 8259) requires that every object member name, i.e., every key, be a string enclosed in double quotes, so keys like {"host": "router1"} are valid while {host: "router1"} is not. Option D is correct because JSON defines exactly six value types — string, number, object, array, boolean (true/false), and null — and the literal keyword null is the valid representation of the null data type, commonly used in Junos automation payloads to indicate an absent or empty value. Option A is incorrect because JSON strings must use double quotes; single quotes are not valid JSON (they are only tolerated by some lenient parsers such as Python's ast.literal_eval or YAML). Option B is incorrect because standard JSON has no comment syntax at all, so a '#' character would be invalid — comments are only available in JSON5, JSONC, or YAML. Option E is incorrect because JSON forbids trailing commas after the last element of an array or the last member of an object, and such input will fail strict parsing.

Answer

Single quotes can be used interchangeably with double quotes for strings.

Answer

JSON supports inline comments starting with the '#' symbol.

Answer

Trailing commas are permitted in both arrays and objects.

Question 2

An engineer writes a Python script that loads a JSON configuration file using the json.load() method. The file contains configuration parameters for a Junos device. If the JSON file contains a trailing comma at the end of the last element in an array, what will happen when the script executes?

Accepted Answer

The script will raise a JSONDecodeError.. Standard JSON specification is strict and does not allow trailing commas. Attempting to parse it will raise a json.decoder.JSONDecodeError.

Answer

The script will successfully parse the file and ignore the trailing comma.

Answer

The script will throw a TypeError during execution.

Answer

The script will convert the trailing comma into a null value automatically.

Question 3

An automation engineer is troubleshooting a Junos REST API script that intermittently fails with HTTP 401 Unauthorized errors when retrieving operational data. The script uses HTTP Basic Authentication with a valid username and password. The engineer confirms that the credentials are correct and that the REST API is enabled. What is the most likely cause of the intermittent failures?

Accepted Answer

The device is configured to use RADIUS authentication, and the RADIUS server is occasionally unreachable.. Intermittent 401 Unauthorized errors with valid credentials often stem from external authentication server issues. When a Junos device is configured to use RADIUS or TACACS+ for user authentication, temporary server unreachability can cause authentication failures. The REST API uses the device's configured authentication methods, so an unreachable RADIUS server would result in 401 responses.

Answer

The script is exceeding the maximum number of concurrent REST API sessions, causing new requests to be rejected with 401.

Answer

The device's clock is out of sync with the authentication server, causing token-based authentication to fail.

Answer

The REST API requires the use of a session cookie instead of Basic Authentication for operational requests.

Question 4

A Python automation script parses a Junos telemetry stream in JSON. The JSON payload uses integer keys in a dictionary (e.g., {443: 'HTTPS'}). When loaded into Python using json.loads(), what data type do the dictionary keys become?

Accepted Answer

They are converted to Python string objects.. JSON specification dictates that object keys must be strings. When json.loads() parses an object, any keys (even if numeric-looking) are converted to Python strings.

Answer

They are converted to floating-point numbers.

Answer

They remain integer objects.

Answer

The parser raises a KeyError because JSON keys must be alphabetic.

Question 5

A Python script using PyEZ loads a configuration from a file and commits it on a Junos device. The commit fails with a `CommitError` exception. You need to retrieve the specific error message returned by the device. Which method or attribute should you use to obtain the detailed error text?

Accepted Answer

`exception.errs`. When a commit fails, PyEZ raises `CommitError` with an `errs` attribute containing a list of error details from the device. Iterating over `exception.errs` provides the specific commit error messages. Other attributes like `message`, `detail`, or `response` are not the correct way to retrieve these details.

Answer

`exception.detail`

Answer

`exception.message`

Answer

`exception.response`

Question 6

When designing an automation workflow that uses the Junos REST API for configuration management, which THREE practices ensure robust execution? (Choose three)

Accepted Answer

Configure HTTPS (jpagent https) to encrypt credentials and configuration payloads in transit.. Option A is correct because the Junos REST API is exposed over HTTPS via the jpagent (Juniper Web Agent) service, so enabling HTTPS (jpagent https) ensures that credentials and configuration payloads are encrypted in transit rather than sent in cleartext. Option B is correct because the REST API requires the client to declare the payload format with the proper Content-Type header (for example, application/json for JSON or application/xml for XML); an incorrect or missing header causes the request to be rejected or misparsed. Option D is correct because robust automation must inspect HTTP response status codes — 200 for successful GETs, 201 for created resources, and 204 for successful operations with no content — to confirm the request succeeded before proceeding. Option C is not appropriate because GET requests are read-only and rebooting the Routing Engine after each one would be disruptive and unnecessary. Option E is not appropriate because the REST API exchanges structured JSON or XML over HTTP, not raw VT100 terminal escape sequences, which belong to interactive CLI sessions.

Answer

Always reboot the Routing Engine after every GET request.

Answer

Send raw VT100 terminal escape sequences inside the HTTP body.

Question 7

You are writing a Python script that converts a Junos operational state output from XML (via NETCONF) into JSON. The XML structure contains sibling elements with the same tag name. When converted naively, how do standard XML-to-JSON conversion libraries (like xmltodict) typically represent these repeated sibling elements in the resulting JSON dictionary?

Accepted Answer

As a JSON array containing multiple objects.. Conversion libraries like xmltodict represent repeated sibling XML elements as a JSON array (list) to preserve all instances under a single key.

Answer

By appending numeric indexes to every key name automatically.

Answer

By raising a DuplicateElementException.

Answer

By overwriting previous elements so only the last element is retained.

Question 8

An automation engineer wants to log structured data from a Junos device automation run. The Python script formats a dictionary into a JSON string and prints it. However, the engineer wants all keys sorted alphabetically to ensure consistent log diffing. Which parameter accomplishes this in json.dumps()?

Accepted Answer

sort_keys=True. The sort_keys parameter in json.dumps() sorts the output of dictionaries by key alphabetically.

Answer

keys_sort=True

Answer

alphabetize=True

Answer

order='alphabetical'

Question 9

Which data serialization formats are natively supported by the Junos REST API for both input and output payloads?

Accepted Answer

JSON and XML. The Junos REST API natively supports both JSON and XML data formats for interacting with operational and configuration data.

Answer

CSV and HTML

Answer

JSON and YAML

Answer

YAML and Protocol Buffers

Question 10

An engineer needs to represent an ordered list of IP addresses in a YAML configuration file for a Junos automation playbook. Which valid YAML syntax correctly defines a sequence of items?

Accepted Answer

ip_addresses:
  - 192.168.1.1
  - 192.168.1.2. In YAML, lists or sequences are represented using a hyphen followed by a space (-) at the beginning of each line.

Answer

ip_addresses = {192.168.1.1, 192.168.1.2}

Answer

ip_addresses: [192.168.1.1: 192.168.1.2]

Answer

ip_addresses:
  * 192.168.1.1
  * 192.168.1.2

Question 11

What is the primary benefit of using structured data formats (such as XML, JSON, or YAML) over unstructured CLI text output in Junos automation?

Accepted Answer

They allow automation scripts to parse device output reliably without relying on brittle regular expressions.. Structured data formats can be easily parsed programmatically without relying on fragile regular expressions.

Answer

Structured data formats take up less memory on the Junos Routing Engine hard drive.

Answer

They eliminate the need to authenticate when connecting via NETCONF or gRPC.

Answer

They automatically convert all IPv4 addresses to IPv6 format.

Question 12

You are using the PyEZ SW utility to install a new Junos image on a device. Which method parameter allows the script to automatically reboot the device after a successful installation?

Accepted Answer

reboot=True. The PyEZ SW utility's install() method accepts a reboot=True parameter that instructs the utility to reboot the device automatically after the Junos image is successfully installed. This is the documented keyword argument in the jnpr.junos.utils.sw.SW class, and it triggers the device reboot as part of the install workflow.

Answer

auto_reboot=1

Answer

reload_after_install=True

Answer

action='reboot'

Question 13

You are developing a Python script using PyEZ to load a configuration onto a Junos device. You need to ensure that the configuration is merged with the existing candidate configuration, and that the load operation does not perform a commit check automatically. Which method should you use to load the configuration from a file?

Accepted Answer

Use `cu.load(path='config.conf', merge=True, check=False)`. The `load` method of the PyEZ `Config` object supports `merge` and `check` parameters. To merge without a commit check, use `merge=True` and `check=False`. The other options either use incorrect parameter names, perform an overwrite, or enable the check. Only the combination of merge and check=False achieves the desired behavior.

Answer

Use `cu.load(path='config.conf', overwrite=True, check=False)`

Answer

Use `cu.load(path='config.conf', merge=True, commit_check=True)`

Answer

Use `cu.load(path='config.conf', action='merge', verify=False)`

Question 14

What is the primary benefit of decoupling network configuration data (YAML/JSON) from presentation templates (Jinja2) in network automation?

Accepted Answer

It allows non-engineers to modify device variables without altering the core template logic, promoting the DRY principle.. Separating data from templates allows the same template to be reused across multiple devices with different data sets, adhering to DRY principles.

Answer

It eliminates the need for any version control system.

Answer

It converts all configuration files into binary format to save disk space.

Answer

It forces the Junos device to run all configuration commits in parallel across all line cards.

Question 15

An engineer needs to retrieve the entire candidate configuration in JSON format from a Junos device using the Junos REST API. Which HTTP header must be included in the GET request to ensure the response is returned in JSON format?

Accepted Answer

Accept: application/json. The Accept header with 'application/json' specifies that the client expects the response to be formatted in JSON.

Answer

Transfer-Encoding: chunked

Answer

Content-Type: text/xml

Answer

X-Junos-Data-Format: json

Juniper Networks Automation and DevOps, Associate (JNCIA-DevOps, JN0-224) JNCIA-DevOps practice test

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Juniper Networks Automation and DevOps, Associate (JNCIA-DevOps, JN0-224) (JNCIA-DevOps) practice questions