JNCIA-DevOps Practice Test 21 — 15 Questions

Question 1

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

Accepted Answer

It supports both JSON and XML data formats.. Option B is correct because the Junos REST API accepts and returns both JSON and XML payloads, letting clients choose the representation via the Content-Type and Accept headers (for example application/json or application/xml). Option D is correct because the REST API is served by the jpagent (Junos REST API agent) daemon, which listens on HTTPS (TCP 443) and handles REST requests on the device. Option A is wrong because the REST API is accessed over standard HTTP/HTTPS with no proprietary C++ client libraries to compile. Option C is wrong because REST is stateless and uses HTTP/HTTPS requests, not a persistent SSH session per transaction. Option E is wrong because TCP 830 is used by NETCONF over SSH, not by the REST API, which uses HTTPS on port 443.

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 2

An automation engineer is using the Junos XML API over SSH to load a configuration snippet into the candidate datastore. The engineer wants to ensure that the configuration is merged with the existing candidate configuration. Which RPC and attribute should be used?

Accepted Answer

with action='merge'. In the Junos XML API, configuration is loaded using the RPC. The 'action' attribute controls how the configuration is integrated; 'merge' merges the new configuration with the existing candidate configuration. Other actions like 'replace' or 'override' would not achieve a merge. NETCONF's is not used in the Junos XML API over SSH context.

Answer

<load-configuration> with action='replace'

Answer

<commit-configuration> with action='merge'

Answer

<edit-config> with operation='merge'

Question 3

An automation engineer is tasked with implementing a REST API client that authenticates to a Junos device. The engineer must choose an authentication method supported by the Junos REST API and ensure that credentials are transmitted securely. Which two statements are correct about authentication for the Junos REST API? (Choose two.)

Accepted Answer

Authentication can be performed using a session cookie obtained from a login RPC.. The Junos REST API supports HTTP Basic Authentication, where credentials are base64-encoded and sent in the Authorization header. It also supports session-based authentication via a login RPC that returns a cookie. Both methods require HTTPS for secure transmission. OAuth 2.0 and API keys are not natively supported. Credentials are not sent in plain text by default; base64 encoding is not encryption, so HTTPS is essential.

Answer

API keys generated on the Junos device can be used in place of passwords.

Answer

Credentials are sent in plain text by default, so HTTPS is optional.

Answer

OAuth 2.0 tokens are natively supported for authentication.

Question 4

You are writing a PyEZ script that must connect to a Junos device and run several RPCs, but you need the connection to automatically recover if the NETCONF session drops during a long-running task. Which PyEZ connection parameter should you configure to enable this behavior?

Accepted Answer

Set `auto_probe=30` in the `Device` constructor to periodically verify the session and reconnect if needed.. The `auto_probe` parameter in the PyEZ `Device` constructor enables automatic session health checks at a specified interval. When set to a non-zero value, PyEZ periodically probes the NETCONF session and reconnects if it has dropped, which is essential for long-running automation tasks that must survive transient network issues. Other parameters like `port` or context managers do not provide this recovery capability.

Answer

Pass `auto_probe=0` to the `Device` constructor to disable session probing.

Answer

Set `port=22` in the `Device` constructor to use SSH instead of NETCONF.

Answer

Use the `Device` context manager (`with Device(...) as dev:`) to ensure the session is closed properly.

Question 5

You are developing a PyEZ script that loads a configuration snippet onto a Junos device. You want to ensure the configuration is merged with the existing candidate configuration and then committed. Which sequence of PyEZ methods should you use?

Accepted Answer

`dev.load_config()` then `dev.commit()`. The PyEZ `load_config()` method loads a configuration snippet into the candidate configuration, merging it with existing configuration by default. Calling `commit()` then activates the candidate configuration on the device. This two-step sequence is the standard way to apply configuration changes with PyEZ, ensuring that the snippet is merged and committed as required.

Answer

`dev.load_config()` then `dev.commit_check()` then `dev.commit()`

Answer

`dev.load()` then `dev.commit()`

Answer

`dev.load_config(merge=False)` then `dev.commit()`

Question 6

You are writing a PyEZ script to retrieve the configured hostname from a Junos device. You want to use the simplest method that returns the hostname as a string without parsing XML manually. Which PyEZ feature should you use?

Accepted Answer

Access `dev.facts['hostname']` after opening the device connection.. PyEZ automatically populates a dictionary of facts when the device connection is established. The `dev.facts` dictionary includes common values such as `hostname`, `model`, `version`, and `serialnumber`. Accessing `dev.facts['hostname']` is the simplest and most direct way to obtain the configured hostname as a string, avoiding manual XML parsing or additional RPC calls.

Answer

Instantiate a `Table` and `View` for the system configuration and extract the hostname field.

Answer

Use `dev.rpc.get_software_information()` and extract the hostname from the response.

Answer

Call `dev.rpc.get_config()` and parse the XML response for the hostname element.

Question 7

An automation engineer is designing a data model for Junos device inventory that will be serialized to JSON and consumed by multiple tools. The engineer wants to include a null value, a boolean, and a string that contains a colon and a space. Which TWO statements correctly describe JSON serialization rules that apply to this model? (Choose two.)

Accepted Answer

A JSON null value is represented by the literal null, and a JSON boolean is represented by the literals true or false, all without quotation marks.. JSON strings use double quotation marks and escape embedded double quotes with a backslash. The literals null, true, and false are unquoted and map to Python None and bool. Colons and spaces inside strings need no escaping, and comments or trailing commas are not permitted in standard JSON.

Answer

JSON object keys must be unique and must always be enclosed in single quotation marks to distinguish them from values.

Answer

JSON permits comments and trailing commas, so the inventory model can include annotations after each field for documentation.

Answer

A JSON string containing a colon and a space must escape both characters with a backslash to remain valid.

Question 8

A network team uses a CI/CD pipeline to manage Junos device configurations. After a developer merges a change to the main branch, the pipeline is triggered automatically. Which DevOps principle is primarily demonstrated when the pipeline deploys the tested configuration to production devices without manual intervention?

Accepted Answer

Continuous delivery. Continuous delivery is the practice of automatically deploying validated changes to production after passing tests, which matches the scenario where the pipeline deploys configurations without manual intervention. Continuous integration is limited to merging and testing, while Infrastructure as Code is about defining infrastructure in code, and continuous monitoring is about observing systems. The automated production deployment is the defining characteristic here.

Answer

Infrastructure as Code

Answer

Continuous integration

Answer

Continuous monitoring

Question 9

You are writing a PyEZ script that must retrieve interface statistics from a Junos device. You want to use a predefined PyEZ Table to avoid writing custom parsing logic. Which predefined Table should you use to get operational status and statistics for all interfaces?

Accepted Answer

`InterfaceTable`. PyEZ includes predefined Tables that simplify retrieving operational data. `InterfaceTable` is the standard Table for interface information, providing operational status, statistics, and configuration attributes for all interfaces. It abstracts the underlying XML RPCs and returns a structured dictionary, making it ideal for scripts that need interface statistics without custom parsing.

Answer

`ConfigTable`

Answer

`PhyPortTable`

Answer

`EthPortTable`

Question 10

An automation engineer is using the Junos XML API over NETCONF to load a configuration change into the candidate datastore. The engineer wants to ensure that the change is committed automatically only if the candidate configuration passes a validation check. Which NETCONF operation should the engineer use to validate the candidate configuration before committing?

Accepted Answer

. The operation is the standard NETCONF method to check a configuration datastore for errors without applying changes. In Junos, this corresponds to the 'commit check' functionality. Using on the candidate datastore ensures the configuration is syntactically and semantically correct before a commit is attempted, reducing the risk of a failed commit in production.

Answer

<edit-config>

Answer

Answer

<check>

Question 11

An engineer is designing a Junos automation solution that requires programmatic access to retrieve operational data and configuration from devices. The solution must use a standardized, vendor-neutral protocol that supports capabilities exchange and transactions. Which protocol should be used?

Accepted Answer

NETCONF. NETCONF is the IETF-standard protocol designed for network configuration and management, offering capabilities exchange, transactional changes, and structured data retrieval. SNMP is for monitoring, RESTCONF is RESTful but less transactional, and CLI over SSH is not standardized. For a vendor-neutral, transactional automation solution on Junos, NETCONF is the correct choice.

Answer

CLI over SSH

Answer

SNMP

Answer

RESTCONF

Question 12

You are writing a PyEZ script that needs to handle exceptions when connecting to a Junos device and executing RPCs. Which TWO exceptions are raised by PyEZ when authentication fails or when the device is unreachable? (Choose two.)

Accepted Answer

`ConnectTimeoutError`. PyEZ defines a set of exceptions for connection-related failures. `ConnectAuthError` is raised when authentication fails, and `ConnectTimeoutError` is raised when the connection attempt times out due to an unreachable device or network issue. These two exceptions directly address the scenarios of authentication failure and unreachability, making them the correct choices.

Answer

`RpcError`

Answer

`PermissionError`

Answer

`ConfigError`

Question 13

A network automation team is using Junos PyEZ to retrieve interface statistics from a device. They need to ensure that the script can handle multiple devices concurrently and that each device connection is properly closed after the operation. Which approach should they take?

Accepted Answer

Use the Device class with the 'with' statement inside a ThreadPoolExecutor.. To handle multiple devices concurrently while ensuring proper connection closure, use ThreadPoolExecutor to run tasks in parallel, and within each task, use a context manager (with statement) to create and automatically close a Device connection. This ensures each device gets its own connection and that resources are released. The other options either lack concurrency or misuse a single Device object.

Answer

Use a single Device object and call open() and close() manually for each device.

Answer

Use the PyEZ 'multi' module to connect to all devices and retrieve data.

Answer

Use the Device class with a context manager for each device in a loop.

Question 14

A network automation engineer is using the Junos XML API over NETCONF to make configuration changes. The engineer wants to ensure that if the commit fails, the candidate configuration is automatically rolled back to its previous state without manual intervention. Which NETCONF operation should the engineer use to achieve this?

Accepted Answer

with a element and a value.. A confirmed commit using with and a timeout automatically rolls back if a confirming commit is not received within the timeout period. This is ideal for automation scripts that need to ensure configuration changes do not persist if something goes wrong. It provides a safety net without manual intervention, unlike explicit rollback or discard operations.

Answer

<rollback> operation with a rollback number.

Answer

<discard-changes> operation after a failed commit.

Answer

with a element.

Question 15

An automation engineer writes a Python script that reads a Junos configuration exported as JSON and uses json.loads to parse it. The script then searches for a key named "interfaces". The JSON document contains two objects at the same nesting level, each with an "interfaces" key, because the configuration was merged from two sources. What will json.loads produce, and how should the script handle it?

Accepted Answer

The parser keeps only the last occurrence of "interfaces" for that object, so the script loses the first source's data unless the original JSON is restructured to use unique keys or an array.. When a JSON object contains duplicate names, Python's json.loads keeps the last occurrence and discards earlier ones without warning. The script must avoid duplicate keys by restructuring the data, such as placing each source's interfaces in a separate array element, so no information is lost during parsing.

Answer

The parser raises a ValueError because JSON forbids duplicate keys, so the script must catch the exception and merge the two sources manually.

Answer

The parser stores both occurrences and exposes them through a special duplicate key accessor that the script can iterate over.

Answer

The parser combines both values into a Python list under the single "interfaces" key, preserving data from both sources automatically.