JNCIA-DevOps Practice Test 14 — 15 Questions

Question 1

An automation engineer needs to retrieve the operational status of all interfaces from a Junos device using the Junos REST API over HTTPS. The device is configured with the REST API enabled and the engineer has valid credentials. Which HTTP request accomplishes this task?

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

Accepted Answer

GET https://<device>/rest/interface-information. The Junos REST API exposes operational RPCs under the /rest/ URI path. To retrieve interface operational status, an automation tool sends a GET request to /rest/interface-information. GET is the correct HTTP method for read-only retrieval, and no additional parameters are needed for a full interface listing. Other paths like /rpc/ belong to the XML API, and using POST for retrieval is incorrect.

Answer

POST https://<device>/rest/interface-information

Answer

GET https://<device>/rest/conf/show-interfaces

Answer

POST https://<device>/rpc/get-interface-information

Question 2

A network automation team is using the Junos REST API to manage configurations on a fleet of Junos devices. They need to ensure that configuration changes are applied atomically and that they can roll back if an error occurs. They decide to use the REST API to load a configuration, commit it, and then verify the commit. Which sequence of REST API calls should they use to load a configuration snippet, commit it, and then confirm the commit was successful?

Accepted Answer

POST to /rest/rpc/load-configuration with the configuration data, then POST to /rest/rpc/commit, then check the HTTP status code and response body of the commit call for success indicators. To load, commit, and verify a configuration via the Junos REST API, you perform a POST to the load-configuration RPC with the configuration data, then a POST to the commit RPC. The commit response includes an HTTP status code and a body that indicates success or failure. Checking this response is the most direct way to confirm the commit succeeded. Additional calls like get-configuration or get-commit-information are not necessary for verifying the commit operation itself.

Answer

POST to /rest/rpc/load-configuration with the configuration data, then POST to /rest/rpc/commit, then GET /rest/rpc/get-configuration to verify the applied configuration

Answer

POST to /rest/rpc/load-configuration, then POST to /rest/rpc/commit, then GET /rest/rpc/get-commit-information

Answer

POST to /rest/rpc/load-configuration, then POST to /rest/rpc/commit-check, then POST to /rest/rpc/commit

Question 3

Which of the following valid JSON values represents a boolean true state?

Accepted Answer

true. JSON (RFC 8259) defines boolean literals as lowercase 'true' and 'false' only. Any other casing or quoting is invalid JSON or represents a different type, so 'true' is the only valid boolean true value among the options.

Answer

True

Answer

"true"

Answer

TRUE

Question 4

Which TWO benefits does NETCONF provide over traditional screen-scraping CLI automation? (Choose two)

Accepted Answer

Structured data representation (XML) that eliminates the need for complex regular expression parsing.. Option A is correct because NETCONF encodes configuration and state data in structured XML (per RFC 6241), so management applications can consume well-defined elements and namespaces instead of brittle screen-scraping with regular expressions against human-oriented CLI output. Option D is correct because NETCONF defines formal RPC transaction semantics, including candidate datastores, commit/rollback operations, and standardized error reporting via <rpc-error> elements, which CLI scraping cannot guarantee. Option B is wrong because NETCONF is a configuration protocol and does not generate physical fiber cabling diagrams. Option C is wrong because NETCONF still requires authentication (commonly SSH per RFC 6242), so it does not eliminate credentials. Option E is wrong because NETCONF does not compress payloads into binary audio streams or reduce bandwidth requirements in that manner.

Answer

Automatic generation of physical fiber cabling diagrams.

Answer

Elimination of any need for authentication credentials.

Answer

Requirement for lower bandwidth links by compressing all payloads into binary audio streams.

Question 5

Which TWO benefits are gained by applying DevOps principles to Junos network management? (Choose two)

Accepted Answer

Consistent, repeatable deployments through automation and version control. Option C is correct because DevOps principles applied to Junos network management emphasize infrastructure-as-code, where configurations are stored in version control systems (e.g., Git) and deployed through automation tools such as Ansible, PyEZ, or Junos Terraform provider, yielding consistent and repeatable deployments. Option E is correct because DevOps fundamentally breaks down silos between teams, fostering shared ownership and improved collaboration between network engineers and software developers through shared tooling, CI/CD pipelines, and common repositories. Option A is incorrect because documentation remains essential in DevOps environments; automation and version control supplement, but do not eliminate, documentation requirements. Option B is incorrect because physical console cables are not mandated by DevOps principles; out-of-band management may still be used for recovery, but DevOps does not require a console cable on every device. Option D is incorrect because DevOps explicitly moves away from exclusive manual CLI configuration toward programmatic, automated configuration via NETCONF, REST API, or Junos automation frameworks.

Answer

Elimination of all network documentation requirements

Answer

Mandatory requirement for physical console cables on every device

Answer

Exclusive reliance on manual CLI configuration commands

Question 6

What Jinja2 feature allows you to include the contents of another template file into your main configuration template?

Accepted Answer

{% include 'filename.j2' %}. Jinja2's {% include 'filename.j2' %} statement renders the contents of another template file inline at that point in the parent template. This is the standard mechanism for modularizing templates — common config blocks (e.g., standard interface settings, SNMP communities) can be stored in separate files and included where needed. The included template shares the parent's variable context.

Answer

{% insert 'filename.j2' %}

Answer

{% import 'filename.j2' %}

Answer

Question 7

You are writing a Python automation script that processes configuration data. The script reads a YAML file containing Junos firewall filters, modifies them, and writes them back out. However, you notice that all the original comments in the file are stripped out in the output. What is the fundamental reason for this behavior in standard PyYAML dump operations?

Accepted Answer

Comments are stripped during parsing because they are not part of the YAML data model.. PyYAML parses YAML files into abstract syntax trees (AST) or Python native data structures, discarding comments during the parsing phase because comments are not part of the data model.

Answer

The yaml.safe_dump() function explicitly deletes comments for security reasons.

Answer

YAML specification mandates that all comments are ephemeral and cannot be serialized.

Answer

Comments must be re-injected using the 'preserve_comments=True' parameter.

Question 8

A Python automation script extracts routing table entries from a Junos device. The data structure contains deeply nested dictionaries and lists. The engineer needs to perform a deep copy of this deserialized JSON structure before modifying it. Which Python module provides the deepcopy function needed to duplicate nested containers safely?

Accepted Answer

copy. The 'copy' module in the Python standard library provides the deepcopy() function, which recursively clones nested dictionaries and lists.

Answer

os

Answer

sys

Answer

json

Question 9

What is the primary function of a version control system (VCS) like Git in a Junos automation workflow?

Accepted Answer

To track configuration history, enable collaboration, and provide a single source of truth for network designs.. A VCS tracks changes over time, enabling collaboration, rollback, and audit trails.

Answer

To act as a high-speed packet forwarding engine for BGP routes.

Answer

To compile Python automation scripts into binary executables.

Answer

To monitor real-time CPU utilization on Junos routing engines.

Question 10

When writing a Python script to interact with a Junos device via PyEZ, you receive an object representing RPC output. You want to serialize a custom Python class instance containing device metadata into JSON, but calling json.dumps() raises a TypeError. What is the standard approach to resolve this?

Accepted Answer

Pass a custom serialization function to the 'default' parameter in json.dumps().. The json module does not know how to serialize custom Python object instances by default. You must provide a custom serialization function and pass it to the 'default' parameter of json.dumps().

Answer

Use yaml.safe_dump() instead, which natively serializes all custom Python classes.

Answer

Convert the object into an XML string before calling json.dumps().

Answer

Modify the global sys.path variable to include the custom class definition.

Question 11

What type of brackets enclose an array in a JSON document?

Accepted Answer

Square brackets ([ ]). Arrays in JSON are enclosed within square brackets ([ and ]).

Answer

Curly braces ({ })

Answer

Angle brackets (< >)

Answer

Parentheses (( ))

Question 12

Which TWO characteristics describe JSNAPy snapshot operations? (Choose two)

Accepted Answer

It saves captured operational data into snapshot files for later comparison.. Option C is correct because JSNAPy's core function is to capture operational state (for example, via 'show' commands defined in a YAML file) and store that output into snapshot files, which serve as the reference data for later checks. Option E is correct because JSNAPy's primary use case is comparing snapshots — typically a post-change snapshot against a baseline pre-change snapshot — to detect configuration or operational drift, using commands like 'jsnapy --check' or 'jsnapy --snapcheck'. Options A, B, and D are incorrect: JSNAPy does not compile Jinja2 templates into CLI commands (that is the role of tools like Jinja2 templating with PyEZ or Junos PyEZ config utilities), it does not replace PyEZ as the NETCONF RPC library (JSNAPy actually relies on PyEZ under the hood), and it does not modify the active configuration database automatically — it only reports differences and never commits changes.

Answer

It compiles Jinja2 configuration templates directly into Junos CLI commands.

Answer

It replaces PyEZ as the primary library for executing NETCONF RPC calls.

Answer

It modifies the active configuration database automatically upon finding errors.

Question 13

When executing a configuration change via the Junos REST API, what is the role of the HTTP DELETE method?

Accepted Answer

To delete a specific configuration hierarchy or statement from the candidate configuration.. In the context of the Junos REST API, the HTTP DELETE method is used to remove a specific configuration object or subtree, analogous to deleting a statement in the Junos CLI or removing an element in NETCONF.

Answer

To clear operational state counters such as interface packet counters.

Answer

To terminate an active REST API session and revoke the auth token.

Answer

To discard the entire candidate configuration.

Question 14

An automation script attempts to load a configuration snippet using NETCONF <edit-config> with operation="delete" on a container statement. What happens if the specified container does not currently exist in the candidate configuration?

Accepted Answer

The device returns a NETCONF rpc-error indicating the node does not exist.. The delete operation fails if the target node does not exist, whereas remove is silent if absent.

Answer

The device ignores the request and returns an OK response.

Answer

The device converts the operation to a merge automatically.

Answer

The device automatically creates the container as an empty object.

Question 15

Which transport protocol is mandated by RFC 6241 as the standard secure connection mechanism for NETCONF when operating in typical Junos enterprise automation environments?

Accepted Answer

SSH. RFC 6241 specifies NETCONF over Secure Shell (SSH) as the standard secure transport protocol.

Answer

HTTPS

Answer

gRPC

Answer

TLS