JNCIA-DevOps Junos REST API Practice Test 4 — 15 Questions

Question 1

Which TWO data serialization formats can an automation engineer request using the 'Accept' header in a Junos REST API GET request? (Choose two)

Accepted Answer

application/json. The Junos REST API supports content negotiation through the HTTP Accept header, and the two media types it recognizes for structured data responses are application/json (option C) and application/xml (option D); requesting either of these causes the device to return the RPC reply serialized in JSON or XML respectively. JSON is the default and most commonly used format for automation tooling, while XML mirrors the native Junos XML API output, so both are valid and correct. The remaining options are not supported by the Junos REST API: application/yaml (A) is not a media type Junos negotiates, text/csv (B) is not a serialization format the API emits, and application/octet-stream (E) denotes an opaque binary stream rather than a structured serialization format.

Answer

application/yaml

Answer

text/csv

Answer

application/octet-stream

Question 2

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 3

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 4

An administrator configures the Junos REST API service. By default, which TCP port does the device listen on for secure HTTPS REST requests?

Accepted Answer

3443. The default TCP port for secure HTTPS requests in the Junos REST API daemon (jpagent) is port 3443.

Answer

443

Answer

8080

Answer

830

Question 5

Which THREE statements correctly contrast the session handling of NETCONF versus the Junos REST API? (Choose three)

Accepted Answer

NETCONF maintains a persistent, stateful connection over an SSH session with capability exchanges.. Option A is correct because NETCONF operates over a persistent SSH transport (typically TCP port 830) and establishes a stateful session that begins with a hello message exchanging capabilities between client and server. Option D is correct because the Junos REST API authenticates each request individually using standard HTTP headers (such as Authorization with Basic credentials or an X-Auth-Token) rather than relying on an interactive shell session. Option E is correct because the Junos REST API follows the stateless HTTP request/response model, where each transaction is independent and no session context is retained between calls. Option B is incorrect because NETCONF does not use HTTP or port 80; it runs over SSH, and HTTP is the transport for REST, not NETCONF. Option C is incorrect because NETCONF sessions do not expire every 30 seconds based on keystrokes; they persist until explicitly closed or timed out by configured idle limits.

Answer

NETCONF requires an HTTP web server running on port 80 to maintain session state.

Answer

NETCONF sessions automatically expire every 30 seconds if an interactive keystroke is not received.

Question 6

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. The Junos REST API exposes operational RPCs under the /api/operational/rpc/ path, and software package information is retrieved via the get-software-information RPC. This endpoint returns details about installed packages, versions, and related state. The other options either target configuration hierarchies or use non-existent REST paths.

Answer

/api/configuration/system/software

Answer

/netconf/rpc/software

Answer

/api/v1/packages/status

Question 7

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.. HTTP 415 Unsupported Media Type means the server refuses to process the request because the payload's media type is not supported. In the Junos REST API, the client must send a Content-Type header (e.g., 'application/json' or 'application/xml') that matches the payload format. If the header is missing or set to something the device does not accept, the device returns 415.

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.

Question 8

Which Junos configuration hierarchy is used to configure system services parameters related to the REST API agent?

Accepted Answer

set system services jpagent. The jpagent service is configured under the 'set system services jpagent' CLI hierarchy.

Answer

set system rest-api

Answer

set protocols rest

Answer

set management-plane api

Question 9

When an automation engineer queries operational data using the Junos REST API, how does the API format the returned structure if the 'Accept: application/json' header is supplied?

Accepted Answer

As a JSON object representation mirroring the hierarchical XML output of Junos operational RPCs.. When application/json is requested, the Junos REST API translates the native XML operational data structures into structured JSON objects.

Answer

As a single long string containing raw CLI output text.

Answer

As a comma-separated values (CSV) text stream.

Answer

As a binary packet capture file.

Question 10

An engineer is comparing how NETCONF and the Junos REST API handle candidate configuration validation. In NETCONF, the client can issue a <validate> RPC. How is configuration validation typically handled in the Junos REST API workflow?

Accepted Answer

Configuration updates via REST API can include validation parameters or commit-check actions to verify syntax before finalizing.. The Junos REST API supports validation parameters or actions (such as checking candidate syntax during configuration updates or invoking validation actions via commit parameters) to ensure correctness before committing.

Answer

NETCONF validates via XML, while REST API automatically converts invalid syntax into comments.

Answer

Validation requires downloading the entire configuration as a text file and running an external Python syntax checker.

Answer

Validation is impossible in REST API; changes are always applied directly to the forwarding plane immediately.

Question 11

An automation script attempts to connect to the Junos REST API via HTTPS, but the Python script throws an SSL certificate verification error. What is the most appropriate way to resolve this in a development environment while maintaining security best practices?

Accepted Answer

Configure the client application to trust the Junos device's self-signed CA certificate or install a valid enterprise CA certificate on the Junos device.. Self-signed certificates on Junos devices cause SSL verification errors. The best practice is to install the device's CA certificate in the client's trust store, rather than disabling verification globally in production.

Answer

Switch from REST API to NETCONF, which does not use SSL certificates.

Answer

Downgrade the REST API connection from HTTPS to plain HTTP 80.

Answer

Change the Junos system host-name to match the default SSL common name.

Question 12

When using the Junos REST API to configure static routes, how does the JSON payload structure represent list items that can have multiple instances (such as multiple next-hops or static routes)?

Accepted Answer

As JSON arrays containing objects for each list entry.. In the Junos REST API, when a configuration element can have multiple instances (e.g., multiple static routes or next-hops), the JSON payload represents them as a JSON array containing an object for each instance. This allows the API to handle multiple entries in a structured way, aligning with JSON's array syntax.

Answer

As XML CDATA blocks embedded within JSON keys.

Answer

As numerical indexed keys (e.g., 'route-0', 'route-1').

Answer

As a single concatenated string separated by semicolons.

Question 13

Which THREE features are provided by the Junos REST API daemon (jpagent) when running on a Junos device? (Choose three)

Accepted Answer

Translation between REST requests/JSON/XML payloads and Junos configuration/operational structures.. Option B is correct because jpagent's core function is to translate incoming REST requests and their JSON or XML payloads into Junos configuration and operational data structures, allowing the REST API to manipulate the same candidate/active configuration and operational command infrastructure used by the CLI. Option C is correct because jpagent manages the HTTP and HTTPS listeners, including binding to configurable ports (for example via the 'set system services rest http port' or 'https port' configuration), so clients can reach the REST endpoint. Option D is correct because jpagent performs authentication validation for REST requests against local user accounts or external AAA (RADIUS/TACACS+) before allowing access to Junos resources. Option A is incorrect because kernel-level packet forwarding and ASIC line-card optimization are handled by the Packet Forwarding Engine and related hardware/software components, not by the REST API daemon. Option E is incorrect because BGP route reflection is a routing protocol function configured under BGP, not a service provided by jpagent.

Answer

Kernel-level packet forwarding optimization for ASIC line cards.

Answer

Autonomous BGP route reflection across core routing instances.

Question 14

Which statement correctly identifies the relationship between Junos REST API and NETCONF data models?

Accepted Answer

Both protocols leverage the same underlying Junos data models and management infrastructure.. Both Junos REST API and NETCONF leverage the same underlying Junos data models and management infrastructure. The Junos REST API is essentially a RESTful interface to the Junos configuration and operational data, which is modeled using YANG and accessed via NETCONF. Therefore, they share the same data models and management framework.

Answer

REST API bypasses all Junos data models and writes directly to kernel memory.

Answer

NETCONF uses YANG models, whereas REST API uses proprietary relational databases.

Answer

NETCONF is deprecated in favor of REST API for all Junos configuration tasks.

Question 15

Which TWO HTTP response status codes indicate a successful Junos REST API request where data was successfully retrieved or modified? (Choose two)

Accepted Answer

200 OK. Option B (200 OK) is correct because the Junos REST API returns HTTP 200 when a request such as a GET successfully retrieves data or a POST/PUT successfully modifies configuration, with the response body carrying the requested representation or result. Option D (204 No Content) is correct because Junos returns HTTP 204 when an operation succeeds but there is no data to return in the body, such as a successful DELETE or a configuration change with no payload. Option A (404 Not Found) is wrong because it signals the requested resource or URI does not exist, not success. Option C (401 Unauthorized) is wrong because it indicates missing or invalid authentication credentials. Option E (500 Internal Server Error) is wrong because it indicates a server-side failure while processing the request.

Answer

404 Not Found

Answer

401 Unauthorized

Answer

500 Internal Server Error