JNCIA-DevOps Practice Exam 2 — 20 Questions

Question 1

Which Python function deserializes a JSON-formatted string into a native Python dictionary?

Accepted Answer

json.loads(). json.loads() (load string) is used to parse a JSON string into a Python object.

Answer

json.load()

Answer

json.read()

Answer

json.parse()

Question 2

An automation script reads interface names and VLAN IDs from a CSV file and converts each row into a JSON object before sending it to a Junos device REST API. Which Python module is specifically designed to parse CSV (Comma-Separated Values) files?

Accepted Answer

csv. The Python standard library includes the 'csv' module, which provides reader and writer objects for tabular CSV data.

Answer

yaml

Answer

json

Answer

xml

Question 3

Your CI/CD pipeline includes a linters step before deployment. Why is running a linter against YAML or Jinja2 template files critical in a Junos automation workflow?

Accepted Answer

To detect syntax errors, indentation issues, and style violations in template and data files before deployment.. Linters catch syntax errors, formatting inconsistencies, and indentation mistakes before files are processed by automation tools or sent to devices.

Answer

To compile YAML files into Junos microcode for the Packet Forwarding Engine.

Answer

To automatically execute unit tests against live BGP peering sessions.

Answer

To encrypt sensitive passwords stored within plaintext configuration files.

Question 4

A Python script reads a Junos configuration snippet stored in YAML. The configuration uses YAML anchors and aliases to duplicate common routing policy definitions across multiple VRFs. When the script parses the file using yaml.safe_load(), what happens to the anchors and aliases?

Accepted Answer

The parser resolves the anchors and populates the resulting Python dictionary with the referenced data.. yaml.safe_load() fully supports YAML anchors (&) and aliases (*) by default, dereferencing them into identical Python data structures in memory.

Answer

The parser raises a ScannerError because anchors are prohibited in safe mode.

Answer

The aliases are ignored, resulting in empty values for those configuration blocks.

Answer

The parser treats the anchor syntax as literal string data.

Question 5

Which of the following primitive data types is NOT supported natively in JSON?

Accepted Answer

Undefined. JSON does not support undefined, functions, or undefined date types natively. Among standard choices, undefined or complex numbers are absent.

Answer

Number

Answer

String

Answer

Null

Question 6

Which TWO features are supported by YAML but are notably absent in standard JSON? (Choose two)

Accepted Answer

Anchors and aliases for data reuse within the document.. YAML supports comments and anchors/aliases, whereas standard JSON supports neither.

Answer

Native browser execution support without parsing libraries.

Answer

Strict enforcement of double quotes on all string keys.

Answer

Strict indentation-based block scoping.

Question 7

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, arrays are ordered lists of values enclosed in square brackets ([...]).

Answer

String

Answer

Object

Answer

Boolean

Question 8

In a CI/CD pipeline for network changes, what is the role of automated unit testing?

Accepted Answer

To verify that individual configuration modules, templates, or script functions produce expected outputs before integration.. Unit testing validates individual components (like a specific macro, template, or script function) to ensure they produce the expected output.

Answer

To measure the exact fiber cable distance between two data centers.

Answer

To automatically upgrade the Junos OS kernel on all cluster nodes simultaneously.

Answer

To physically test the optical transceiver power levels using laser beams.

Question 9

Which TWO characteristics are true regarding the Junos REST API? (Choose two)

Accepted Answer

It supports both JSON and XML data formats.. The Junos REST API runs on jpagent (default port 3000 for HTTP and 3443 for HTTPS) and natively supports both JSON and XML data formats.

Answer

It requires client-side compilation of proprietary C++ libraries.

Answer

It requires a persistent SSH session for every transaction.

Answer

It runs on TCP port 830 exclusively.

Question 10

Which THREE advanced features or methods are available on a PyEZ Device instance for session management and inspection? (Choose three)

Accepted Answer

dev.timeout property to get or set NETCONF RPC timeout values. PyEZ Device instances provide methods to check connection status, manage timeout values, and inspect capabilities.

Answer

dev.reload_session() for refreshing device facts

Answer

dev.commit_timeout for software installation timing

Question 11

An automation engineer is writing a Python script using Juniper PyEZ to connect to a Junos device. Which context manager approach is best practice to ensure the Device session is properly closed even if an exception occurs?

Accepted Answer

with Device(host="192.168.1.1", user="admin", passwd="secret") as dev:. Using the 'with Device(host=...) as dev:' context manager guarantees that the open() and close() methods are handled automatically, even if runtime errors occur inside the block.

Answer

dev = Device(host="192.168.1.1"); dev.start_session()

Answer

dev = Device(host="192.168.1.1"); dev.open(autoclose=True)

Answer

dev = Device(host="192.168.1.1").connect()

Question 12

An automation engineer wants to retrieve information about all software packages installed on a Junos device using the REST API. Which operational RPC endpoint category is typically targeted?

Accepted Answer

/api/operational/rpc/get-software-information. Software inventory and package information can be retrieved by invoking the 'get-software-information' RPC via the operational RPC URI path.

Answer

/api/configuration/system/software

Answer

/netconf/rpc/software

Answer

/api/v1/packages/status

Question 13

Which TWO configuration steps are required to enable the Junos REST API with basic security settings? (Choose two)

Accepted Answer

set system services jpagent https. To enable the REST API, you must enable the jpagent service and optionally enable HTTPS for secure transport.

Answer

set system netconf secure-mode

Answer

set protocols rest-api state active

Answer

set system services rest enable

Question 14

When managing configuration changes via PyEZ Config utility, which context manager ensures that changes are automatically rolled back if an exception occurs within the block?

Accepted Answer

with Config(dev) as cu:. The 'with Config(dev) as cu:' context manager automatically handles locking, loading, committing, and rolling back on failure.

Answer

with Config(dev, mode='private') as cu:

Answer

try: cu.lock() except: cu.rollback()

Answer

cu.commit(rollback_on_error=True)

Question 15

Which TWO error response categories or HTTP status codes are commonly returned by the Junos REST API when client requests are malformed or unauthorized? (Choose two)

Accepted Answer

401 Unauthorized. 401 Unauthorized is returned for bad or missing credentials, and 400 Bad Request is returned for malformed payload syntax.

Answer

202 Accepted

Answer

504 Gateway Timeout

Answer

100 Continue

Question 16

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.. REST API provides structured data formats (JSON/XML), deterministic API contracts with HTTP status codes, and programmatic resource addressing, whereas screen-scraping relies on fragile text parsing.

Answer

Strict enforcement of synchronous modal CLI configuration blocks.

Answer

Requirement for VT100 terminal emulation buffers.

Question 17

When developing Python scripts that utilize PyEZ and Jinja2, which THREE best practices ensure robust and maintainable automation code? (Choose three)

Accepted Answer

Using the PyEZ Config context manager to ensure locks are released and rollbacks occur on error. Best practices include proper exception handling, using context managers, and separating templates from logic.

Answer

Hardcoding administrative passwords inside template files for easy rendering

Answer

Avoiding device.close() calls to keep network sessions open permanently

Question 18

An engineer is designing an automated failover script that needs to discard candidate configuration changes made via the Junos REST API. How should this discard action be performed?

Accepted Answer

Send a request to the configuration discard/rollback endpoint or invoke the discard-changes RPC via the REST API.. Discarding candidate changes in the Junos REST API is performed by invoking the discard configuration RPC or action endpoint equivalent to the NETCONF <discard-changes/> RPC.

Answer

Send an HTTP GET request with ?action=reset.

Answer

Issue an HTTP DELETE request to the root /api/configuration path.

Answer

Restart the routing engine process (RE switchover).

Question 19

When comparing the Junos REST API workflow to the NETCONF protocol workflow, which characteristic is unique to the REST API?

Accepted Answer

It requires the use of HTTP verbs such as GET, POST, PUT, and DELETE.. The Junos REST API uses standard HTTP methods (GET, POST, PUT, DELETE) and standard data formats like JSON or XML over HTTP/HTTPS, unlike NETCONF which uses XML over a dedicated TCP port (830).

Answer

It exclusively transmits data encoded in protocol buffers.

Answer

It uses connection-oriented stateful sessions over port 830.

Answer

It mandates the use of YANG schema files for every single RPC.

Question 20

An engineer is troubleshooting a script that updates Junos configuration via the REST API. The payload is sent as JSON, but the device returns a 415 Unsupported Media Type error. What is the root cause?

Accepted Answer

The Content-Type header provided in the HTTP request is missing or specifies an unsupported media type.. A 415 Unsupported Media Type error indicates that the Content-Type header sent in the HTTP request does not match what the Junos REST API daemon expects for processing configuration payloads (such as application/vnd.juniper.netconf.config+json or application/json).

Answer

The device is running out of memory buffers.

Answer

The user account does not have permission to execute PUT requests.

Answer

The target resource URI path does not exist on the device.