JNCIA-DevOps Junos Automation Stack And DevOps Concepts — 15 Questions

Question 1

What is the primary benefit of using structured data formats (such as XML, JSON, or YAML) over unstructured CLI text output in Junos automation?

Accepted Answer

They allow automation scripts to parse device output reliably without relying on brittle regular expressions.. Structured data formats can be easily parsed programmatically without relying on fragile regular expressions.

Answer

Structured data formats take up less memory on the Junos Routing Engine hard drive.

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They eliminate the need to authenticate when connecting via NETCONF or gRPC.

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They automatically convert all IPv4 addresses to IPv6 format.

Question 2

In a DevOps pipeline managing Junos devices, an engineer implements 'Infrastructure as Code' (IaC). Which practice best exemplifies this methodology when applied to Junos routing policies?

Accepted Answer

Defining routing policies in Jinja2 templates and YAML data files, committing them to Git, and automatically pushing them via Ansible playbooks.. IaC defines infrastructure in declarative configuration files stored in version control, allowing automated testing and deployment.

Answer

Writing custom Python scripts that use regex to parse 'show route' outputs on the fly.

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Manually logging into each router via SSH during a maintenance window to type out policy-options statements.

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Using dynamic routing protocols like BGP to automatically advertise prefixes without human intervention.

Question 3

An engineer needs to explain the primary advantage of treating network configurations as code in a modern DevOps workflow. Which principle best describes this approach?

Accepted Answer

Storing configurations in a version control system to track history, enable rollbacks, and facilitate collaboration.. Treating network configurations as code allows infrastructure to be version-controlled, repeatedly deployed, and tested just like software code.

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Immutable infrastructure deployment where devices are replaced rather than updated manually.

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Compiling the network CLI commands into binary machine code before executing them on Junos devices.

Answer

Automating the complete removal of the command-line interface in favor of graphical topology builders.

Question 4

You are configuring a CI/CD pipeline for Junos network deployments. The pipeline must validate the syntax of generated candidate configurations against a physical or virtual Junos device before committing them to production. Which stage of the CI/CD pipeline does this validation step represent?

Accepted Answer

Continuous Integration validation stage. Checking syntax and logic prior to production deployment is a core part of the Continuous Integration (CI) validation and testing stage.

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Continuous Deployment stage

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Continuous Monitoring stage

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Infrastructure Provisioning stage

Question 5

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.

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

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To automatically execute unit tests against live BGP peering sessions.

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To encrypt sensitive passwords stored within plaintext configuration files.

Question 6

A network engineer is using Git for version control of Junos configurations. During a peer review on a pull request, a merge conflict arises because two engineers modified the same interface description line in different branches. What is the correct procedure to resolve this conflict in Git?

Accepted Answer

Manually edit the conflict markers in the affected configuration file, stage the resolved file, and complete the merge commit.. Git marks the conflicting lines in the file, requiring manual editing to choose the correct changes or combine them, followed by staging and committing the resolution.

Answer

Reboot the Junos routing engine to clear the Git repository cache and force a fast-forward merge.

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Run the 'git force-merge' command to automatically discard the older branch's changes.

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Use 'git reset --hard' on the remote repository to delete both conflicting branches entirely.

Question 7

Which Junos automation architecture component provides standardized, model-driven interfaces using NETCONF and gRPC/gNMI to manage and monitor Junos devices?

Accepted Answer

Junos XML API and schema definitions. Junos API and data modeling components like NETCONF and gRPC provide structured, programmatic access to the Junos control plane.

Answer

The Junos CLI pipe filter 'match' command

Answer

Proprietary screen-scraping CLI scripts running in a crontab daemon

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The physical console cable attached to the Routing Engine

Question 8

An automation script connects to a Junos device and attempts to load a candidate configuration using NETCONF. The script needs to ensure that if any part of the configuration fails validation, the entire transaction is discarded and the candidate database is left untouched. Which NETCONF capability or tag should be utilized?

Accepted Answer

The candidate configuration database lock combined with atomic transaction semantics provided by NETCONF and operations.. NETCONF supports robust transaction handling, ensuring that configuration changes are validated as a block and rolled back on error.

Answer

The SNMP trap notification daemon running on port 162

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The <rollback> RPC with an explicit configuration revision number

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The 'cli -s' force-override flag in an SSH execution session

Question 9

An automation engineer is designing a deployment strategy for Junos devices using Git branches. Which branching strategy model aligns best with continuous delivery where feature branches are merged frequently into a shared integration branch that automatically triggers staging tests?

Accepted Answer

Trunk-based development where developers merge small, frequent changes into a central main branch that drives automated pipelines.. GitFlow and trunk-based development describe common branching models; trunk-based development or short-lived feature branches with continuous integration are standard for modern DevOps.

Answer

Creating a separate permanent branch for every physical router in the network and never merging them.

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Locking the master branch for 12 months while developing a single monolithic configuration update offline.

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Using tag-based releases exclusively without utilizing any version control branches.

Question 10

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.

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The Git repository automatically rejects the push citing syntax errors.

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

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

Question 11

Which Junos automation tool utilizes NETCONF over SSH by default to manage network devices using Python libraries or configuration management frameworks?

Accepted Answer

Junos PyEZ. Ansible, PyEZ, and NETCONF clients communicate with Junos using NETCONF over SSH by default.

Answer

The local Junos shell (sh) utility

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Wireshark packet analyzer

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Junos Space Network Management Platform GUI

Question 12

When managing Junos configuration changes in a team environment, why is atomic configuration rollback capability crucial during automated deployments?

Accepted Answer

It ensures that either all configuration statements in a transaction are applied successfully or none are, preventing partial/corrupt states.. Atomic rollbacks ensure that if a change set fails validation or causes a network fault, the system can revert cleanly to the previous working state without partial application.

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It compresses the configuration database to save NVRAM storage space.

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It allows the router to dynamically rewrite Python scripts into C++ for faster execution.

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It automatically backs up the entire Junos OS image to an external TFTP server.

Question 13

In the context of network DevOps, what is the purpose of implementing idempotency in automation scripts or playbooks targeting Junos devices?

Accepted Answer

To ensure that running the same configuration task multiple times produces the exact same desired state without making redundant changes if already applied.. Idempotency ensures that running the same automation task multiple times yields the same result without making unintended changes if the state is already correct.

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To encrypt all configuration payloads using AES-256 before transport.

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To ensure that every script execution generates a completely random new configuration to test device resilience.

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To force the Junos Routing Engine to reboot every time a script is executed.

Question 14

Which protocol is natively used by Junos XML management APIs to provide structured, session-oriented configuration and operational data exchange?

Accepted Answer

NETCONF. NETCONF is the session-oriented protocol used for Junos XML management.

Answer

FTP

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Syslog

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Telnet

Question 15

An enterprise uses Git for tracking Junos configurations. An engineer wants to see the exact line-by-line history of changes made to a specific routing policy file over the past month, including who made each change. Which Git command should they use?

Accepted Answer

git blame or git log -p . 'git blame' shows what revision and author last modified each line of a file, while 'git log' shows commit history.

Answer

git history --routing-policy

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git diff --author

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git status --verbose