JNCIA-DevOps Practice Test 18 — 15 Questions

Question 1

Which term describes the practice of continuously building, testing, and validating software or network configurations in an automated pipeline?

Accepted Answer

CI/CD (Continuous Integration / Continuous Deployment). Continuous Integration / Continuous Deployment (CI/CD) describes automated building and testing.

Answer

Manual Change Advisory Board (CAB) review

Answer

Cold-boot disaster recovery

Answer

Static physical cable patching

Question 2

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. Option A (401 Unauthorized) is correct because the Junos REST API returns HTTP 401 when a client request lacks valid authentication credentials, such as a missing or incorrect Authorization header or invalid username/password, which is the standard response for unauthorized access. Option B (400 Bad Request) is correct because the Junos REST API returns HTTP 400 when the client request is malformed, for example due to invalid JSON/XML payload syntax, incorrect URI formatting, or unsupported parameters that the server cannot parse. Option C (202 Accepted) is not correct because it is a success-class status indicating the request was accepted for processing, not an error for malformed or unauthorized requests. Option D (504 Gateway Timeout) is not correct because it indicates an upstream server failed to respond in time, which is an infrastructure/proxy timeout rather than a client malformation or authorization error. Option E (100 Continue) is not correct because it is an informational interim response used with the Expect: 100-continue mechanism, not an error category returned for malformed or unauthorized requests.

Answer

202 Accepted

Answer

504 Gateway Timeout

Answer

100 Continue

Question 3

You are writing a Python automation script that reads a Junos configuration file in JSON format. The JSON file contains duplicate keys within the same object scope. According to the JSON specification RFC 8259, how should a conforming JSON parser handle duplicate keys?

Accepted Answer

Behavior is undefined by the specification; typically the last defined key-value pair overwrites previous ones in Python dictionaries.. RFC 8259 explicitly states that JSON object names SHOULD be unique, but does not mandate parser behavior when duplicates occur — the behavior is undefined by the specification. In practice, Python's json module (and most parsers) keeps the last occurrence, silently overwriting earlier values in the resulting dictionary.

Answer

Both values are automatically combined into a JSON array under that key.

Answer

Duplicate keys are prohibited, and compliance checks will reject the file pre-parsing.

Answer

The parser must raise a fatal JSONDecodeError immediately.

Question 4

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 csv module in Python is specifically designed to read and write CSV files. It provides functionality to parse rows of comma-separated values into lists or dictionaries, handling quoting and delimiter variations. This makes it the correct choice for reading interface names and VLAN IDs from a CSV file before converting to JSON.

Answer

yaml

Answer

json

Answer

xml

Question 5

You are writing a script that performs multiple configuration changes inside a single PyEZ Config context. How can you verify that the candidate configuration has syntax errors before committing it?

Accepted Answer

cu.validate(). The PyEZ Config utility provides the `cu.validate()` method to check the candidate configuration for syntax errors before committing. It performs a commit check on the device, returning any errors without actually committing the configuration, allowing the script to verify correctness inside a Config context.

Answer

cu.test_syntax()

Answer

cu.verify()

Answer

cu.check()

Question 6

An engineer receives a YAML configuration snippet for a PyEZ automation script, but the script fails with a parser error. Upon inspection, the error is caused by improper indentation levels. Which rule must be strictly followed regarding indentation in YAML syntax?

Accepted Answer

Spaces must be used for indentation, and tabs are strictly forbidden.. YAML requires the use of space characters for indentation. Tab characters are strictly forbidden for indentation purposes.

Answer

Indentation is completely optional if curly braces are used.

Answer

Tabs must be used consistently for every level of indentation.

Answer

Indentation must always be exactly four spaces per level.

Question 7

When executing a NETCONF request, you specify but omit any filtering tags. What is returned in the ?

Accepted Answer

The complete configuration contained within the candidate datastore.. Omiting filter tags on a <get-config> request returns the entire contents of the specified configuration datastore.

Answer

An rpc-error stating that a filter is mandatory.

Answer

Only the differences between candidate and running configurations.

Answer

Only the top-level system hierarchy statements.

Question 8

An administrator issues an edit-config RPC with default-operation="replace" targeting the candidate datastore. What is the impact on the existing configuration on the Junos device?

Accepted Answer

The entire target configuration datastore is replaced by the configuration provided in the RPC payload.. The replace operation overwrites the entire target configuration datastore with the configuration provided in the RPC message.

Answer

The configuration is merged, and any conflicting nodes generate a validation error.

Answer

The candidate datastore is cleared, and only the default factory configuration is loaded.

Answer

Only the specific leaf nodes provided in the RPC are updated; everything else remains intact.

Question 9

You are reviewing a pull request that updates Junos interface configurations using Jinja2 templates. The template contains a conditional statement checking an interface speed variable. What happens if the variable is undefined during template rendering?

Accepted Answer

Jinja2 raises an undefined error and halts template rendering unless default filters or conditional checks are used.. Jinja2 raises an UndefinedError by default when an undefined variable is evaluated in a template, unless configured otherwise or handled with defined tests.

Answer

The Git repository automatically rejects the push citing syntax errors.

Answer

Junos automatically ignores the missing variable and applies default factory settings.

Answer

The target Junos router enters rescue mode due to corrupted NETCONF RPC messages.

Question 10

Which statement best describes the primary architectural difference between NETCONF and the Junos REST API?

Accepted Answer

NETCONF is a connection-oriented RPC protocol over SSH, while Junos REST API is a resource-oriented web API over HTTP/HTTPS.. NETCONF is a session-oriented, connection-oriented protocol running over SSH (port 830) using XML-encoded RPCs. The Junos REST API is a stateless (at the HTTP layer) resource-oriented web API running over HTTP/HTTPS (port 3000/3443) supporting JSON and XML.

Answer

NETCONF only supports JSON, while REST API only supports XML.

Answer

There are no architectural differences; REST API is simply an XML parser for NETCONF.

Answer

NETCONF is a web-based stateless API, whereas REST API requires a persistent SSH session.

Question 11

An automation engineer needs to pretty-print a JSON payload in the Linux terminal for debugging Junos telemetry. Which built-in Python command-line utility can be invoked to validate and pretty-print a JSON file?

Accepted Answer

python3 -m json.tool filename.json. The command 'python3 -m json.tool filename.json' invokes the built-in json.tool module, which validates and pretty-prints JSON from a file or stdin. It is a standard utility available in any Python 3 installation.

Answer

python3 -m yaml.format filename.json

Answer

python3 -c 'import json; json.format()'

Answer

netconf-console --pretty filename.json

Question 12

An engineer writes a Python script using ncclient to push changes to a Junos device. After sending the configuration via <edit-config>, the script needs to make the changes active without dropping the NETCONF session lock prematurely or requiring a separate explicit commit RPC if candidate workflows are bypassed. However, using standard candidate datastore workflow, what is the exact RPC required to activate the candidate configuration?

Accepted Answer

. The RPC is used to commit the candidate configuration to the running configuration datastore in Junos.

Answer

<apply-changes/>

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<save-config/>

Answer

<push-running/>

Question 13

An automation engineer wants to verify the syntax of a large YAML playbook before executing it against a production Junos device. Which python one-liner command can be run in the terminal to quickly check if the file is syntactically valid YAML?

Accepted Answer

python3 -c 'import yaml, sys; yaml.safe_load(open(sys.argv[1]))' config.yaml. Running python3 -c 'import yaml, sys; yaml.safe_load(open(sys.argv[1]))' filename.yaml attempts to parse the file and will report any syntax errors.

Answer

yaml --validate config.yaml

Answer

netconf-console --check config.yaml

Answer

python3 -m json.tool config.yaml

Question 14

When writing Python automation scripts for Junos using PyEZ, which THREE objects or methods are commonly used for device interaction and configuration management? (Choose three)

Accepted Answer

Config (from jnpr.junos.utils.config) to handle configuration transactions. Option E is correct because the Device class from jnpr.junos is the core PyEZ object that opens and manages the NETCONF session to a Junos device, providing the transport used by all other operations. Option C is correct because Config from jnpr.junos.utils.config wraps configuration transactions, allowing methods like load(), commit(), rollback(), and diff() to apply candidate configurations safely. Option D is correct because Fact, loaded via the factory Loader from jnpr.junos.factory.factory_Loader, retrieves structured device facts such as hardware model, Junos version, and serial number for inventory and automation logic. Option A is not part of PyEZ and is unrelated to Junos device interaction, and Option B is not a real PyEZ object or method and would be a destructive, nonsensical operation.

Answer

Microsoft_Excel_Workbook for direct spreadsheet parsing

Answer

Kernel_Panic_Trigger to deliberately crash the router

Question 15

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.. Automated unit testing in a CI/CD pipeline verifies that individual components, such as configuration modules, templates, or script functions, produce the expected outputs. This ensures that each part works correctly before integration, catching errors early in the development cycle.

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.