Cisco 200-901 DevNet Associate (DEVASC) Exam Practice Test

Test-Driven Development (TDD) is a software development approach where tests are written before the code that needs to be tested.

TDD Process:

Write a Test: Start by writing a test for a new feature or functionality.

Run the Test: Run the test, which should fail initially since the code hasn’t been written yet.

Write Code: Write the minimum amount of code required to pass the test.

Run Tests Again: Run the tests again to ensure they pass.

Refactor: Refactor the code while ensuring the tests still pass.

Advantages:

Early Bug Detection: Bugs are detected early in the development cycle.

Better Design: Promotes writing cleaner, more modular code.

Documentation: The tests themselves serve as documentation for the code.

Writing and running tests before writing the actual code ensures that the code meets the specified requirements and functions correctly.

References:

TDD Overview: Test-Driven Development

1 – C, 2 – D, 3 – B, 4 - A

When a developer encounters many lines of code doing repetitive tasks, refactoring the code to use functions is a standard practice. This reduces code duplication and enhances readability and maintainability. Functions encapsulate repetitive logic, making the code cleaner and more organized.

Test-Driven Development (TDD) is a software development approach where tests are written before the actual code. The process follows these steps:

Write a test before writing code (B): Developers write tests for a new function or feature before implementing it. This ensures that the tests define what the code is supposed to do.

Enable code refactoring (A): Because tests are written first, TDD supports continuous refactoring of the code. Developers can confidently improve and clean up code, knowing that existing functionality is verified by the tests.

1 – A, 2 – C, 3 – B

The two protocols used to apply configuration changes on a Cisco IOS XE device are:

RESTCONF: A REST-like protocol used for accessing data defined in YANG, using the datastore concepts defined in NETCONF. It allows the application of configurations and retrieval of state information using HTTP methods.

NETCONF: A protocol defined to manage configurations and monitor devices. It uses remote procedure calls (RPCs) to apply changes in a structured data format defined by YANG.

References: Cisco DevNet Associate Certification Guide, Chapter on Network Management Protocols including NETCONF and RESTCONF.

An artifact repository is a key component in a CI/CD pipeline, used to manage binary files and other artifacts produced and consumed during the build process. It helps in organizing and tracking these artifacts through various stages of the pipeline.

Provides Traceability, Search, and Management of Binary Files:

Artifact repositories store binary files and metadata, allowing developers to trace back to the source and understand the context in which an artifact was produced.

These repositories often come with search functionalities to locate specific versions of binaries quickly.

Examples include JFrog Artifactory, Nexus Repository, and AWS CodeArtifact.

Stores Files Needed and Generated During the Build Process:

Artifact repositories store intermediate and final build outputs, dependencies, libraries, and other necessary files.

These repositories support the storage and distribution of build artifacts, ensuring consistent deployment in different environments (e.g., staging, production).

A firewall is a network device that monitors incoming and outgoing traffic and decides whether to allow or block specific traffic based on a defined set of rules.

Function of a Firewall:

Traffic Monitoring: It continuously monitors all traffic passing through it.

Rule-Based Filtering: It applies predefined security rules to allow or deny traffic.

Protection: It protects networks from unauthorized access and cyber threats.

Comparison with Other Devices:

Switch: A network device that connects devices within a LAN and uses MAC addresses to forward data to the correct destination.

Load Balancer: Distributes network or application traffic across multiple servers to ensure no single server becomes overwhelmed.

Reverse Proxy: A server that sits in front of web servers and forwards client requests to those web servers.

Therefore, a firewall is the correct answer because it specifically monitors and filters network traffic based on security rules.

References:

Cisco Firewalls Overview: Cisco Firewall Products

1 – D, 2 – F, 3 – A, 4 – E, 5 – B, 6 – G, 7 - C

The HTTP status code 400 (Bad Request) is used by a REST API to indicate that the server cannot or will not process the request due to something that is perceived to be a client error (e.g., malformed request syntax, invalid request message framing, or deceptive request routing).

The HTTP status code 200 indicates successful execution of a request.

Status Code 200:

Meaning: OK - The request has succeeded. The meaning of the success depends on the HTTP method:

GET: The resource has been fetched and is transmitted in the message body.

HEAD: The headers are in the message body.

POST: The resource describing the result of the action is transmitted in the message body.

TRACE: The message body contains the request message as received by the server.

Comparison with Other Codes:

404 - Not Found: The server can’t find the requested resource.

405 - Method Not Allowed: The request method is known by the server but is not supported by the target resource.

500 - Internal Server Error: The server encountered an unexpected condition that prevented it from fulfilling the request.

Thus, the status code 200 indicates that the request was successful.

References:

HTTP Status Codes: MDN Web Docs

The issue shown in the sequence diagram is an HTTP 401 Unauthorized response. This suggests that the authentication credentials provided are incorrect or improperly formatted. The correct format for the credentials in a cURL command should be without quotes around the username and password. Hence, changing -u 'cisco

' to -u cisco

resolves the issue.

Cisco Intersight API interactions can be encoded in XML or JSON and require an API key in the HTTP header for authentication: This statement is true. Cisco Intersight APIs support both XML and JSON formats for API interactions. API keys are used in the HTTP header to authenticate requests.

UCS manager API interactions are XML-encoded and require a cookie in the method for authentication: This statement is true. Cisco UCS Manager APIs typically use XML for encoding interactions, and a session cookie is required for authentication after an initial login request.

Cisco Intersight API: Uses either XML or JSON formats and requires API keys for authentication.

Cisco UCS Manager API: Utilizes XML format and relies on session cookies for authentication.

References:

Cisco Intersight API Documentation

Cisco UCS Manager API Documentation

When configuring a Cisco IOS XE device using RESTCONF, the default data-encoding method is XML. RESTCONF is a protocol used to access configuration data and operational data using a REST-like API, and it uses XML as the default encoding method for data exchange.

XML: Used as the default encoding method for RESTCONF.

x-form-encoding: Not used by RESTCONF.

YANG: A data modeling language used to model configuration and state data manipulated by NETCONF and RESTCONF, but not an encoding method.

YAML: Not used by RESTCONF.

1 – A, 2 – B, 3 – D, 4 – C

A firewall is a network security device that monitors and controls incoming and outgoing network traffic based on predetermined security rules. It establishes a barrier between a trusted internal network and untrusted external networks, such as the Internet. Firewalls can be hardware-based or software-based. They are essential for network security as they help protect against threats and unauthorized access.

References:

Cisco DevNet Associate Exam Topics: Network Fundamentals (understand the role and function of firewalls in network security)

Cisco Networking Basics: Network Security Devices and Firewalls (explains the functions and importance of firewalls)

The HTTP POST method is used by both Meraki and Webex Teams APIs to send webhook notifications. Webhooks are a way for applications to provide other applications with real-time information. The POST method is used to send data to a server to create/update a resource. In the case of webhooks, the POST request carries the event data to the endpoint URL specified by the receiving service. More details on webhooks can be found in the Meraki Webhook Documentation and Webex Teams Webhooks.

The HTTP POST method is used by both Meraki and Webex Teams APIs to send webhook notifications. Webhooks are a way for applications to provide other applications with real-time information. The POST method is used to send data to a server to create/update a resource. In the case of webhooks, the POST request carries the event data to the endpoint URL specified by the receiving service. More details on webhooks can be found in the Meraki Webhook Documentation and Webex Teams Webhooks.

A version control system (VCS) is essential for managing changes to source code over time. One significant advantage of a VCS is:

Facilitates resolving conflicts when merging code (Option C):

Version control systems like Git track changes made by different developers and provide tools to manage and merge these changes. When multiple developers work on the same codebase, conflicts can arise if they make changes to the same lines of code. A VCS helps in identifying these conflicts and provides mechanisms to resolve them, ensuring that the final merged code is consistent and error-free.

References:

Git Documentation on Merging

Cisco DevNet Version Control Systems

YANG (Yet Another Next Generation) is a data modeling language used to model configuration and state data manipulated by the NETCONF protocol. Here are two advantages of YANG-based approaches for infrastructure automation:

Multi-platform vendor abstraction (Option B):

YANG provides a standardized way to model configuration and state data, enabling multi-platform vendor abstraction. This means that network engineers can write configurations and management scripts that work across different network devices from different vendors, as long as they adhere to the YANG model. This reduces the complexity and increases the interoperability in multi-vendor environments.

Designed to reflect networking concepts (Option C):

YANG is specifically designed to reflect networking concepts and constructs, making it intuitive and effective for defining network configurations and states. The hierarchical structure of YANG models aligns well with the structure of network configurations, allowing for precise and clear definitions of network elements and their relationships.

References:

Cisco YANG Overview

IETF YANG

Test-Driven Development (TDD) is a software development approach where tests are written before writing the actual code. The steps involved in TDD are:

Write a test for the new functionality.

Run the test and see it fail (because the functionality is not yet implemented).

Write the minimum code necessary to make the test pass.

Refactor the code while keeping the test passing.

Option B is the correct answer because refactoring code while it is covered by existing tests is a key aspect of TDD. The existing tests ensure that the functionality remains correct even after refactoring.

References:

Cisco DevNet Associate Exam Topics: Software Development and Design (understanding TDD methodology)

"Test-Driven Development by Example" by Kent Beck (standard reference on TDD)

The Ansible playbook provided in the exhibit performs the following tasks:

Uses the ios_command module to issue the show conf command on the CISCO_ROUTER_01 device.

Registers the output of the command into the variable config.

Copies the content of config.stdout[0] (the first line of the command output) to a file in /etc/ansible/configs/.

This sequence of tasks effectively backs up the running configuration of the router by capturing the current configuration output and saving it to a file.

References:

Ansible ios_command Module

Ansible Playbook Basics

A 401 Unauthorized error indicates that the request has not been applied because it lacks valid authentication credentials for the target resource. To resolve this error when making an HTTP GET request to retrieve data using RESTCONF on a CSR 1000V, you need to ensure that the correct authentication credentials (username and password) are provided.

The error message JSON-PARSE-ERROR and Unexpected character ('"' (code 34)) indicates a JSON formatting issue. Specifically, there is likely an incorrect character or misplaced quote within the JSON structure. Properly formatting the JSON payload and ensuring all fields are correctly quoted and syntax rules are followed will resolve this error.

A – E, B – D, C – B, D – C, E – A, F – F

Option A correctly creates a handle instance using the UcsHandle class from the UCS SDK in Python. The correct instantiation requires providing the IP address, username, password, port number, and secure connection parameters as per the documented API.

The correct code snippet is:

from ucsmsdk.ucshandle import UcsHandle

handle = UcsHandle("10.1.2.254", "admin", "password", port="443", secure=True)

This snippet matches the API documentation requirements:

ip: The IP or hostname of the UCS Server.

username: The username as configured on the UCS Server.

password: The password as configured on the UCS Server.

port: The port number to be used during the connection.

secure: True for a secure connection.

References:

UCS Python SDK Documentation (provides details on how to use UcsHandle)

Cisco DevNet Associate Exam Topics: Infrastructure and Automation (understanding how to use APIs and SDKs for automation)

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The Bash script shown performs the following actions:

It reads a directory name into the variable ndir.

It enters a loop that continues as long as the directory specified by ndir exists (-d "$ndir" checks if a directory exists).

Inside the loop, it changes the current directory to ndir.

Once the loop exits (when a directory with the name ndir no longer exists), it creates a new directory with the name stored in ndir.

Thus, the script ensures that it continues to navigate into directories with the given name until it finds one that does not exist, and then creates it.

To ensure the result set is returned in reverse chronological order based on when messages were entered, we need to use the sortBy parameter with the value lastactivity. This parameter sorts the rooms by their last activity timestamp, ensuring the most recent rooms are listed first.

Example:

GET /v1/rooms?sortBy=lastactivity

References:

Cisco Webex Teams API Documentation (explains query parameters and their usage in API calls)

Cisco DevNet Associate Exam Topics: APIs and Automation (understanding how to utilize query parameters to retrieve data)

In REST architecture, the stateless constraint indicates that no client context should be stored on the server between requests. Each request from the client to the server must contain all the information needed to understand and process the request.

Stateless: Ensures that each request is independent and contains all necessary information.

Uniform interface: Defines a standard way of interacting with resources.

Cacheable: Responses must define whether they are cacheable to improve performance.

Client-server: Separates the client and server roles.

The docker run -p 3000:5000 command maps port 3000 on the host to port 5000 on the Docker container. This means that any process on the host that wants to access the service running inside the container should connect to port 3000 on the host. The service inside the container listens on port 5000, but from the host's perspective, it will be accessed via port 3000. More information on Docker port mapping can be found in the Docker documentation.

Cisco Advanced Malware Protection (AMP) provides APIs that can be used to obtain a list of vulnerable software on user devices. AMP for Endpoints offers extensive capabilities for threat detection and response, including the ability to query for vulnerabilities. These APIs allow developers to integrate vulnerability information into their applications, enabling proactive security measures. Detailed information on using AMP APIs can be found in the Cisco AMP for Endpoints API documentation.

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The Python function shown in the exhibit performs the following operations:

It defines a function get_result().

Inside the function, it sets the url variable to the Cisco DNA Center (DNAC) API endpoint for authentication tokens.

It makes a POST request to the specified URL with HTTP Basic Authentication using the credentials DNAC_USER and DNAC_PASSWORD.

The response from the POST request is expected to be in JSON format.

It extracts the value associated with the key 'Token' from the JSON response.

Finally, it returns this token.

This function's purpose is to obtain and return an authorization token from the Cisco DNA Center API, which can be used for subsequent API requests.

The "time exceeded in-transit" ICMP message is generated when a packet's Time-To-Live (TTL) field reaches zero before reaching its destination. This usually occurs when the packet has traversed too many routers (hops), indicating that the destination is too far away or there is a routing loop causing excessive hops.

TTL Field: Every IP packet has a TTL field which decrements by 1 every time it passes through a router. When TTL reaches zero, the packet is discarded and an ICMP "time exceeded" message is sent back to the sender.

Network Latency: High latency or excessive hops can cause packets to expire in transit, leading to this ICMP message.

Solution as below

To request a service ticket using the APIC-EM REST API, the following Python script can be used:

Import necessary libraries (requests and json).

Define the APIC-EM controller's URL.

Create the payload with the username and password.

Set the header to specify the content type as JSON.

Make a POST request to the /api/v1/ticket endpoint with the payload and header.

Parse the JSON response to extract the service ticket.

References:

Cisco DevNet Associate Exam Topics: APIs and Automation (understanding how to use REST APIs)

APIC-EM API Documentation (provides details on endpoints and request structures)

When a REST API limits the amount of data returned in a response, it often uses pagination. Pagination breaks the response into smaller, more manageable chunks, allowing the client to retrieve the data in multiple requests.

Pagination: Limits the number of records returned in a single response, requiring additional requests to retrieve subsequent records.

Payload limit: Restricts the size of the response payload but is not the specific feature for controlling record count.

Rate limiting: Controls the number of requests a client can make in a given time period.

Service timeouts: Define how long the server will wait for a request to complete before timing out.

1 – E, 2 – B, 3 – D, 4 – A

A default gateway serves as an access point or IP router that a networked computer uses to send information to a computer in another network or the internet. It is essentially the forwarding node that routes traffic from a local network to other networks. When an IP packet's destination is not within the local network and no specific route is defined in the routing table, the packet is sent to the default gateway.

To extract the value "172.16.0.11" from the given JSON data, you need to navigate through the JSON structure using the correct keys and indices. The JSON structure provided is as follows:

"items": [{

"kind": "object#NetworkObj",

"selfLink": "https://10.201.230.5/api/objects/networkobjects/db01 ",

"name": "db01",

"host": {

"kind": "IPv4Address",

"value": "172.16.0.11"

},

"objectId": "db01"

}]

}

Access the 'items' key: This gives you a list containing one object.

Access the first object in the 'items' list: Using the index [0].

Access the 'host' key: This contains the 'kind' and 'value' keys.

Access the 'value' key within the 'host' object: This gives you the required value "172.16.0.11".

Thus, the correct way to access the value "172.16.0.11" is data['items'][0]['host']['value'].

References:

JSON Parsing in Python: Python JSON Module

Cisco DevNet Documentation: DevNet JSON Handling

The primary function of the default gateway in a network is to forward traffic to different subnets. It acts as an intermediary that routes traffic from a local network to other networks, including the Internet.

Default Gateway: A router or network device that routes traffic from a local subnet to other subnets or networks. It serves as an access point or IP router that a networked computer uses to send information to a computer in another subnet or network.

References: Cisco DevNet Associate Certification Guide, Chapter on Networking Basics and IP Routing.

Network programmability allows for automated, scalable, and replicable network provisioning and management. This reduces the need for manual configuration, minimizes human errors, and enables the implementation of consistent network policies across multiple devices and environments. By leveraging APIs and automation tools, network operations become more efficient and can easily adapt to changes in the network.

Cisco IOS XE supports model-driven programmability using protocols such as gNMI (gRPC Network Management Interface). gNMI is a protocol that provides a way to manage and configure network devices using a standardized approach to data models and APIs.

Model-Driven Telemetry: gNMI is used for streaming telemetry data from network devices.

Configuration Management: It allows for the configuration of network devices using standardized YANG models.

The error message in the cURL response indicates that the request requires a valid access token set in the Authorization request header. This error is common when the authorization header is either missing or the token provided is incorrect or expired.

To resolve this issue, ensure the correct Bearer token is included in the Authorization header, formatted as follows:

-H "Authorization: Bearer YOUR_ACCESS_TOKEN"

References:

Cisco DevNet Associate Exam Topics: Security and Access Management (understanding how to handle API tokens and authorization)

Cisco Webex API Documentation (details on how to properly format API requests and handle authorization)

Statement B: One of the routers has two connected serial interfaces.

This statement is true if the diagram indicates that a router has two serial interfaces. In network diagrams, routers often have multiple interfaces to connect different segments or other routers, particularly for WAN connections.

Statement E: The subnet address of PC-B has 18 bits dedicated to the network portion.

If PC-B's subnet is represented by an address such as 192.168.x.x/18, then 18 bits are used for the network portion, leaving 14 bits for host addresses. This aligns with standard subnetting practices where a /18 subnet mask means the first 18 bits define the network, and the remaining bits define host addresses.

For example, a subnet mask of 255.255.192.0 corresponds to /18 in CIDR notation, indicating that the first 18 bits are for the network portion.

Incorrect Statements:

Statement A: PC-A and PC-B are in the same subnet.

This statement can be evaluated based on the IP addresses and subnet masks provided for PC-A and PC-B. If they share the same network portion of their addresses and subnet masks, then they are in the same subnet. However, without explicit addresses, this cannot be verified.

Statement C: The subnet of PC-C can contain 256 hosts.

For a subnet to contain 256 hosts, it would need a /24 subnet mask (255.255.255.0), which provides 256 IP addresses (254 usable for hosts). The subnet mask should be examined to determine the validity of this statement.

Statement D: R1 and R3 are in the same subnet.

This depends on the IP addresses and subnet masks assigned to the interfaces on R1 and R3. If they are within the same network range, then they would be in the same subnet.

Since the network diagram is not provided, the verification is based on common networking principles and standard practices in subnetting. For detailed and accurate confirmation, the exact IP addresses, subnet masks, and interface connections need to be reviewed.

A MAC (Media Access Control) address is a unique identifier assigned to a network interface card (NIC) for communications at the data link layer of a network segment. MAC addresses are used within local area networks (LANs) to ensure that data packets are delivered to the correct hardware device. Every network interface on a device, such as a computer, router, or switch, has a unique MAC address.

Agentless configuration management systems, such as Ansible, do not require agents to be installed on the managed hosts. Instead, they leverage existing protocols and services to perform configuration tasks.

Agentless Approach: These systems rely on protocols like SSH (for Unix/Linux) or WinRM (for Windows) to communicate with and manage the hosts.

No Agent Installation: Managed hosts do not need any additional software (agents) installed, which simplifies management and reduces overhead.

Interpreters: They may require the managed hosts to have an interpreter for scripts (e.g., Python) but primarily use existing network protocols for communication.

Option D correctly identifies that agentless configuration management systems use existing protocols to interface with managed hosts.

In the Ansible playbook, the last task uses the apt module with state: absent and purge: yes for the webexbot package. This configuration ensures that the package is uninstalled and all associated configuration files are removed. This is different from a simple uninstall, which would leave configuration files behind.

References:

Cisco DevNet Associate Study Guide: Automation with Ansible (Chapter 7, Section: Ansible Playbook Examples and Syntax).

The primary security issue in this scenario is that API keys are stored in the configuration files. It is a best practice to store sensitive information such as API keys in a secure vault service rather than in configuration files.

A. Communication between the application and the services is not encrypted - Incorrect. The communication is through HTTPS, which is encrypted. B. The database credentials should be stored in the configuration files so that they are secured on the same server - Incorrect. Database credentials should be securely obtained, as mentioned, through a vault service. C. The API keys are stored in the configuration files but should be stored in the vault service - Correct. Storing API keys in configuration files poses a security risk. They should be stored in a secure vault service. D. The synchronization logs should be encrypted and not stored in a relational database - Incorrect. The issue is not about storing logs in a relational database, but rather the storage of API keys in configuration files.

References:

Secure Secrets Management

Best Practices for Storing API Keys

JSON and XML are both used for data interchange, but they have differences in functionality:

JSON: JavaScript Object Notation natively supports arrays and other data structures like objects (dictionaries in Python). JSON is known for being lightweight and easy to parse and is often considered more human-readable due to its simple syntax.

XML: eXtensible Markup Language does not natively support arrays in the same straightforward manner as JSON. Instead, arrays in XML need to be represented using repeated elements, which can be more verbose and complex. XML is highly flexible and supports defining custom tags, but it is generally more complex and less human-readable compared to JSON.

Therefore, JSON's native support for arrays makes it simpler and more efficient for certain data structures compared to XML.

The Python script shown in the exhibit collects CLI arguments, organizes data according to the Cisco-IOS-XE-native YANG model, and utilizes Cisco REST APIs to make configuration changes. The workflow being automated by the script is adding a new route to a device.

A. updating an existing route on the device - Incorrect. The script is adding a new route, not updating an existing one. B. adding a new route to a device - Correct. The script adds a new route using the provided prefix, mask, and IP address. C. including a route on the device and overwriting the current routes - Incorrect. The script does not indicate it overwrites existing routes. D. deleting the route that is passed through the command-line variables - Incorrect. The script is adding a route, not deleting one.

References:

Cisco IOS XE YANG Data Models

Cisco REST API Documentation

The script returns a 401 Unauthorized response, indicating that the request lacks proper authentication. To resolve this, you must include an Authorization header in the HTTP GET request. The value of this header should be the Base64 encoded string of the username and password in the format username:password. This is necessary to authenticate the request and receive a 200 OK response.

References:

Cisco DevNet Associate Study Guide: REST API Authentication Methods (Chapter 7, Section: HTTP Basic Authentication).

VLANs (Virtual Local Area Networks) provide multiple benefits, including segmenting the broadcast domain, which reduces unnecessary traffic and improves network performance. They also enable the logical grouping of devices across different physical Layer 2 switches, enhancing network management and security by isolating traffic between different VLANs.

References:

Cisco DevNet Associate Study Guide: Network Segmentation and VLANs (Chapter 4, Section: Understanding VLANs and Their Benefits).

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An engineer writes a Python script that uses two different API calls to query Cisco DNA Center for the number of interfaces on a device. The engineer notices that the two API calls produce different results. The fewer interfaces returned for the same device when the 'get_all_interfaces' API call is used can be explained by pagination.

A. times out - Incorrect. A timeout would likely result in an error, not fewer results. B. rate limit - Incorrect. Rate limiting would slow down requests but not reduce the number of returned interfaces. C. pagination - Correct. The 'get_all_interfaces' API call might be paginated, meaning it returns results in chunks rather than all at once. D. invalid password - Incorrect. An invalid password would result in an authentication error, not fewer results.

References:

Cisco DevNet DNA Center Platform

API Pagination

The Python script uses nested loops to gather information:

The first loop checks for the "ACME" organization.

If found, it collects information about the networks in that organization.

The second loop checks for the "BLDG21" network.

If found, it gathers information about clients in that network.

This process effectively provides the BLDG21 network information if it is part of the ACME organization.

A developer is creating a script to interact with a REST API service that requires basic authentication. The correct combination of payload and headers using Basic Authentication with the provided Base64 encoded credentials is:

A. This option does not use headers correctly. B. Option B - Correct. This option correctly places the 'Authorization' header in the headers dictionary with 'Basic' authentication. C. This option uses 'Bearer' instead of 'Basic' for the 'Authorization' header. D. This option uses 'Bearer' instead of 'Basic' for the 'Authorization' header.

References:

HTTP Authentication

Base64 Encoding

A reverse proxy can be used to route external requests to different applications on the same host machine using a single public IP address and port. It forwards the requests to the appropriate backend servers based on the request URL or other routing rules.

Single Entry Point: A reverse proxy serves as a single entry point to multiple applications, making it ideal for managing traffic to multiple services hosted on the same machine.

Routing Requests: It can route requests to different internal ports based on the requested URL or other criteria.

Option A is the correct choice as a reverse proxy handles external access to multiple applications on the same host.

Refactoring is done during test-driven development (TDD) to improve the maintainability and readability of the code. After writing tests and ensuring that the code passes those tests, developers refactor to clean up the code, making it more efficient and easier to understand without changing its functionality.

A. to enable larger objects and longer methods - Incorrect. Refactoring aims to simplify and streamline code, not make it larger or more complex. B. to improve maintainability and readability - Correct. Refactoring makes the code easier to maintain and understand. C. to ensure that the previous uses of the objects are explained - Incorrect. This is not the purpose of refactoring. D. to ensure the duplication of essential code - Incorrect. Refactoring seeks to reduce code duplication, not ensure it.

References:

Test-Driven Development by Example

Model-driven programmability offers several benefits:

Model-driven APIs for abstraction and simplification: These APIs provide a higher level of abstraction, making it easier to manage and automate networks.

Models decoupled from transport, protocol, and encoding: This decoupling ensures that the same model can be used with different transport protocols, making the system more flexible and easier to integrate with various technologies.

The docker run command is used to create and start a new container from an image. The -p option maps a port on the host to a port in the container.

Port Mapping: The syntax -p [host_ip:host_port:container_port/protocol] is used to map ports.

Exposing Port 8443: The correct mapping to expose the API on port 8443 and allow external connections is 0.0.0.0:443:8443/tcp, which maps port 443 on the host to port 8443 in the container.

Option B correctly maps the ports and allows external connections.

In the provided Python script, database credentials (DB_USER, DB_PWD) are stored in a JSON configuration file (config.json). While it is common to store configuration and credentials in external files, they should always be encrypted to ensure security.

Secret Management: Storing secrets such as database credentials directly in configuration files in plaintext is a security risk.

Encryption: Secrets must be encrypted to protect them from unauthorized access. This can be achieved using various methods such as encrypting the configuration file itself or using secret management tools.

Best Practices: Always ensure that sensitive information like passwords is encrypted when stored, especially in files that might be part of the source code.

Option C is the correct answer because it emphasizes the necessity of encrypting secrets if they are stored in the user database or configuration files to prevent unauthorized access.

Organizing code into modules allows for code reuse, which simplifies maintenance and improves efficiency. Modules encapsulate specific functionality, making it easier to manage and update. This approach reduces redundancy, as common functions can be written once and reused across multiple programs, leading to more manageable and maintainable codebases.

References:

Cisco DevNet Associate Study Guide: Software Development and Design (Chapter 3, Section: Modular Programming and Code Reuse).

Cisco DNA Center is a comprehensive network management and command center for enterprise networks, providing centralized management, automation, security, and policy enforcement across both wired and wireless networks.

Cisco ACI: Primarily focuses on data center automation and policy enforcement.

Cisco DNA Center: Provides organization-wide automation, security, and policy enforcement capabilities for both wired and wireless networks.

Cisco Umbrella: Offers cloud security services.

Cisco SD-WAN: Focuses on software-defined wide-area networking solutions.

Cisco DNA Center is designed to bring agility and operational efficiency across the entire enterprise network by leveraging advanced automation and assurance capabilities.

Organizing code into modules helps manage large and complex systems by breaking them down into smaller, more manageable pieces. Each module can be developed, tested, and maintained independently, which simplifies the overall development and maintenance process.

The error in the Python code is due to the requests library not being defined, which typically means it hasn't been installed. To resolve this issue, the requests library needs to be installed using the pip install requests command. This will add the necessary module to the Python environment, allowing the code to execute correctly.

In version control systems, code review is typically performed before the code is merged into the main branch. The code review process involves evaluating the changes, ensuring they meet the project's coding standards, and identifying potential issues. This process helps maintain code quality and integrity before integration into the larger codebase.

References:

Cisco DevNet Associate Study Guide: Version Control and Code Review (Chapter 6, Section: Best Practices for Version Control).

The Model-View-Controller (MVC) design pattern provides several advantages, including the ability to present multiple views of the same data to different user groups and the separation of concerns by dividing the application into three interconnected components.

A. to enable multiple views of the same data to be presented to different groups of users - Correct. MVC allows different views to display the same data, enhancing flexibility and usability. B. to provide separation between the view and the model by ensuring that all logic is separated out into the controller - Correct. MVC promotes the separation of concerns, making the application easier to manage and scale. C. to ensure data consistency, which requires that changes to the view are also made to the model - Incorrect. This is not a primary advantage of MVC; changes to the view do not directly affect the model. D. to ensure that only one instance of the data model can be created - Incorrect. This is not a characteristic or advantage of MVC. E. to provide only a single view of the data to ensure consistency - Incorrect. MVC supports multiple views.

References:

MVC Design Pattern

The exhibit shows an example of cross-site scripting (XSS), a security vulnerability where an attacker injects malicious scripts into content from otherwise trusted websites. In this case, the alert function is used to demonstrate the potential for XSS attacks, where user input is improperly sanitized, allowing script execution.

The platform used to programmatically create a space and invite users for collaboration is Cisco Webex.

A. Cisco Intersight - Incorrect. Cisco Intersight is used for infrastructure management. B. Cisco Finesse - Incorrect. Cisco Finesse is used for contact center management. C. Cisco Webex - Correct. Cisco Webex is used for collaboration and includes APIs to create spaces and invite users. D. Cisco UCM - Incorrect. Cisco Unified Communications Manager (UCM) is used for call processing.

References:

Cisco Webex API Documentation

Cisco Webex Teams API

To complete the get_auth_token() function in the script to obtain a valid authentication token using HTTP Basic Authentication, you need to use the requests library correctly. The correct approach involves using the requests.post() method with the HTTPBasicAuth function.

A. resp = requests.post(url, auth=HTTPBasicAuth(DNAC_USER, DNAC_PASSWORD)) token = resp.json()['Token'] return token

Correct. This option uses requests.post() and HTTPBasicAuth properly. It retrieves the token from the JSON response.

B. resp = requests.post(url, auth=(DNAC_USER, DNAC_PASSWORD)) token = resp.json()['Token'] return token

Incorrect. This option incorrectly passes the auth credentials as a tuple without HTTPBasicAuth.

C. resp = http.post(url, auth=HTTPBasicAuth(DNAC_USER, DNAC_PASSWORD)) token = resp.json()['Token'] return token

Incorrect. http is not a valid method from the requests library.

D. resp = http.post(url, auth=(DNAC_USER, DNAC_PASSWORD)) token = resp.json()['Token'] return token

Incorrect. This option uses http.post(), which is incorrect.

References:

requests - HTTP for Humans

Cisco DNA Center Platform

The Cisco DevNet API documentation is the primary resource for understanding the meanings of response codes received from REST API calls. It provides comprehensive details about the API endpoints, response codes, and their interpretations, which helps developers troubleshoot and understand the responses they receive.

To ensure the Python code runs successfully, the environment variable WEBEX_TEAMS_ACCESS_TOKEN must be set. This can be done using the export command in a Bash script.

A. define WEBEX_TEAMS_ACCESS_TOKEN=your_access_token_here - Incorrect. define is not a valid Bash command for setting environment variables. B. export WEBEX_TEAMS_ACCESS_TOKEN=your_access_token_here - Correct. This command correctly sets the environment variable for the current session. C. set WEBEX_TEAMS_ACCESS_TOKEN=your_access_token_here - Incorrect. set is not used in this context for setting environment variables in Bash. D. WEBEX_TEAMS_ACCESS_TOKEN=your_access_token_here - Incorrect. This command sets the variable but does not export it to be available to child processes.

References:

Setting Environment Variables in Bash

HTTP status codes in the 2xx range indicate that a request has been received, understood, and processed successfully.

A. 2xx - Correct. This range of status codes indicates successful responses. B. 3xx - Incorrect. This range of status codes indicates redirection messages. C. 4xx - Incorrect. This range of status codes indicates client errors. D. 5xx - Incorrect. This range of status codes indicates server errors.

References:

HTTP Status Codes

To ensure that changes in a file that already exists in a local repository are included in the next Git commit, the git add command must be executed. This command stages the changes in the specified file(s) so they will be included in the next commit.

A. git update - Incorrect. There is no git update command. B. git merge - Incorrect. This command is used to merge branches, not to stage changes. C. git add - Correct. This command stages changes in the working directory to be included in the next commit. D. git rebase - Incorrect. This command is used to reapply commits on top of another base tip.

References:

Git Basics - Recording Changes to the Repository

The diff -u command shows the differences between two files. In the output provided:

Lines with + indicate additions.

Lines with - indicate deletions.

From the exhibit:

There are 8 additions (lines marked with +).

There are no deletions.

The original file was 165 lines long. Adding the 8 new lines results in a total of 173 lines.

When an IP packet does not match any routes in the routing table, it is routed to the default gateway. The default gateway serves as a forwarding host that routes traffic from a local network to other networks or the Internet.

A. firewall - Incorrect. A firewall is a security device, not used for routing unmatched packets. B. load balancer - Incorrect. A load balancer distributes network or application traffic across multiple servers, not used for routing unmatched packets. C. central switch - Incorrect. A switch operates at the data link layer and does not perform IP routing. D. default gateway - Correct. The default gateway is used to route packets that do not match any other route in the routing table.

References:

Cisco Network Fundamentals

To determine the correct JSON snippet for configuring a new interface according to the YANG model, we need to carefully examine both the YANG model definitions and the provided JSON snippets. Here’s a step-by-step explanation:

YANG Model Analysis:

The ietf-interfaces YANG module defines a container interfaces with a list interface.

Each interface has the following important leaves: name, enabled, and description.

The ietf-ip YANG module augments the interface list with a container ipv4, which includes a list address. Each address has the ip and netmask leaves.

Key Elements in JSON:

To configure an interface, the JSON must include the name of the interface, its enabled status, and the IP address configuration.

The structure should reflect the hierarchy defined by the YANG models.

Options Analysis:

Option A:

json

Copy code

"ietf-interfaces:interface": {

"name": "Loopback100",

"enabled": true,

"ietf-ip:ipv4": {

"address": [

{

"ip": "10.255.254.1",

"netmask": "255.255.255.0"

}

]

}

}

This option correctly follows the hierarchy specified in the YANG model. The interface includes name and enabled leaves and augments with ietf-ip:ipv4 which includes the address list with ip and netmask.

Option B:

"ietf-interfaces": {

"interface": {

"name": "Loopback100",

"enabled": true,

"ietf-ip": {

"ipv4": {

"address": [

{

"ip": "10.255.254.1",

"netmask": "255.255.255.0"

}

]

}

}

}

}

This option incorrectly nests interface directly under ietf-interfaces, which does not match the YANG model’s structure.

Option C:

"interface": {

"name": "Loopback100",

"enabled": true,

"ipv4": {

"address": [

{

"ip": "10.255.254.1",

"netmask": "255.255.255.0"

}

]

}

}

This option misses the namespace prefixes ietf-interfaces and ietf-ip required by the YANG model.

Option D:

"ietf-interfaces:interface": {

"name": "Loopback100",

"enabled": true,

"ietf-ip:ipv4:address": [

{

"ip": "10.255.254.1",

"netmask": "255.255.255.0"

}

]

}

This option incorrectly uses ietf-ip:ipv4:address directly, which does not align with the proper hierarchy where address should be nested inside ipv4.

Correct Explanation:

Option A correctly adheres to the YANG model hierarchy and namespace specifications.

It properly nests address within ipv4, which is itself nested within ietf-ip augmentation to interface.

This structure is consistent with how the YANG models define the relationships between the elements.

References:

Understanding of YANG models and their use: Cisco DevNet YANG Introduction

YANG Data Models in NETCONF: RFC 6020

Jitter refers to the variation in packet arrival times, which can cause packets to arrive out of order, leading to choppy audio or dropped parts of a conversation in real-time VoIP applications. Latency and delay refer to the time it takes for a packet to travel from source to destination, and capacity refers to the bandwidth available, but jitter specifically affects the consistency of packet delivery timing, which is critical for VoIP quality.

References:

Cisco DevNet Associate Study Guide: QoS and Network Performance (Chapter 8, Section: Understanding Jitter and Its Effects).

Synchronous API requests and asynchronous API requests differ primarily in how and when the client receives a response from the server.

Synchronous API Request: In a synchronous API call, the client sends a request to the server and waits for a response. The client is blocked during this time, meaning it cannot perform other tasks until the server responds. The key characteristic is that the client is able to access the results immediately after the request is processed. This is suitable for operations that need an immediate response and where the processing time is relatively short.

Asynchronous API Request: In an asynchronous API call, the client sends a request and continues its process without waiting for the server to respond. The server processes the request and sends the response back to the client at a later time. The client might receive a task ID (option A), subscribe to a webhook (option B), or poll for status (option D) to check when the operation is complete.

A VLAN (Virtual Local Area Network) allows devices on one or more LANs to be grouped together as if they were on the same physical network, even if they are not.

Logical Segmentation: VLANs provide logical segmentation of networks, enabling devices to communicate as if they are on the same physical network.

Isolation and Flexibility: They offer isolation and flexibility in network design, improving security and reducing broadcast domains.

Option B is correct as VLANs create logical groupings of devices that communicate as if they are on the same physical LAN.

The HTTP response code 204 No Content indicates that the server successfully processed the request, but there is no content to send in the response. This status code is typically used when a request is successfully handled, but no additional information needs to be returned to the client.

References:

Cisco DevNet Associate Study Guide: HTTP Status Codes (Chapter 7, Section: Common HTTP Response Codes).

pyATS (Python Automation Test System) is a tool developed by Cisco that allows for comprehensive testing of network configurations and automation scripts. It is designed to validate and test changes before they are applied to the production environment, ensuring reliability and reducing the risk of errors.

References:

Cisco DevNet Associate Study Guide: Network Test Automation (Chapter 6, Section: Introduction to pyATS and Its Use Cases).

The Python script in the exhibit interacts with Cisco DNA Center APIs to query devices and execute commands. It collects the results of specific show commands from the devices.

Device Query: The script first queries for devices with the platformId of 'C9500-40X'.

Command Execution: It sends commands (show version, show ip int brief) to these devices.

Result Gathering: The script retrieves and processes the results of the executed commands.

Option A accurately describes the process automated by the script, which is to gather the results of the show version and show ip int brief commands.

In the provided network topology, Device E is positioned between Server 1 and Server 2. Device E, being a Layer 2 switch, will limit traffic between these servers by making forwarding decisions based on MAC addresses. If there are VLANs configured, Device E will ensure that traffic is segregated accordingly, allowing only specific traffic to pass between the servers as defined by the network policies.

References:

Cisco DevNet Associate Study Guide: Network Components (Chapter 2, Section: Switches and Their Role in Network Traffic Management).

When selecting the "best route" for a network device to reach its destination, the considerations include:

Metrics: These are values used by routing protocols to determine the best path to a destination. Metrics can include factors like hop count, bandwidth, delay, load, and reliability.

Administrative Distance: This is a value used to rate the trustworthiness of the source of the routing information. Lower values indicate more trusted routes.

To integrate changes from an existing branch named 'feat00304' into a single commit with the current working primary branch 'prodapp411926287', the git merge --squash command must be used. This command squashes all commits from the feature branch into a single commit before merging.

A. git rebase --merge feat00304 - Incorrect. This command does not perform a squash merge. B. git merge --squash feat00304 - Correct. This command squashes all commits from 'feat00304' into a single commit and then merges it. C. git push --rebase feat00304 - Incorrect. This command is used for pushing changes and rebasing, not for squashing commits. D. git checkout --squash feat00304 - Incorrect. This command is invalid.

References:

Git Merge Squash

The difference between YAML and JSON in terms of data structure representation is that YAML uses indentation to indicate structure, while JSON uses brackets and braces.

A. YAML uses spaces; JSON uses parentheses - Incorrect. JSON does not use parentheses. B. YAML uses indentation; JSON uses brackets and braces - Correct. YAML relies on indentation for structure, whereas JSON uses brackets and braces. C. YAML uses brackets and braces; JSON uses indentation - Incorrect. This is the opposite of the correct statement. D. YAML uses parentheses; JSON uses spaces - Incorrect. Neither format uses these exclusively.

References:

YAML vs. JSON

The provided documentation outlines how to use Basic HTTP Authentication with the Cisco AMP API. The correct method involves encoding the client ID and API key in base64 format and then including them in the authorization header. However, in the given scripts, the use of the requests library’s auth parameter directly with the client ID and API key is also a valid method.

Option A correctly uses the requests library to make an API call with the client ID and API key. This method is supported and valid as per the documentation.

python

Copy code

import requests

amp_client_id = 'alb2c3d4e5f6g7h8i9j0'

amp_login_password = 'l0g1n_p@ssw0rd'

url = 'https://api.amp.cisco.com/v1/version '

request = requests.get(url,

auth=(amp_client_id, amp_login_password))

print(request.json())

Client ID and API Key: amp_client_id and amp_login_password are set with the values provided.

URL: The URL for the AMP API endpoint is correctly set.

GET Request: The requests.get method is used with the auth parameter that takes a tuple of the client ID and API key.

Response: The response is printed in JSON format.

Option B:

Does not use the auth parameter or a header for Basic Authentication, thus it will fail.

Option C:

Uses a single amp_auth_token which does not follow the provided documentation method.

Option D:

Incorrectly uses the auth parameter with a concatenated client ID and API key without specifying Basic Authentication in the header.

References:

Cisco AMP for Endpoints API Documentation

Requests: Authentication

DNS (Domain Name System) is the technology responsible for resolving a host name to an IP address. It translates domain names, which are easier for humans to remember, into IP addresses that are used by network devices to locate and communicate with each other over the internet. When a user types a domain name into a web browser, the DNS server maps it to the corresponding IP address so the browser can load the desired web page.

NTP (Network Time Protocol) is the protocol used for clock synchronization between network devices. It synchronizes the clocks of computers and network devices to ensure that all devices in a network have the same time, which is crucial for logging events, security protocols, and coordinating time-sensitive operations.

The Waterfall model is a linear and sequential approach to software development. In Waterfall, all requirements are specified at the beginning of the project, and each phase (e.g., design, implementation, testing) must be completed before moving on to the next. This makes it less adaptable to changes once the project is underway.

Agile, on the other hand, is an iterative approach that allows for flexible responses to changes in requirements. Agile development is organized into small, incremental cycles called sprints, which typically last 1-4 weeks. During each sprint, a small portion of the project is developed, and changes can be incorporated based on feedback and evolving requirements.

RESTCONF is a protocol used for accessing data defined in YANG, using RESTful principles. It is suitable for retrieving configuration data in JSON format from a Cisco CSR 1000 V instance. RESTCONF allows network devices to be managed using HTTP methods, and it supports both XML and JSON as data formats, making it ideal for outputting device configurations in JSON.

In the provided Python code, the API_PASSWORD is retrieved from the environment variable API_PASSWORD. To set this environment variable in a Bash shell, the correct command to use is export. This command sets the environment variable for the current shell session and any child processes.

Bash Command: export API_PASSWORD=Cisco123!

This command ensures that the environment variable API_PASSWORD is set to "Cisco123!" and can be accessed by the Python script.

References:

Bash export Command

Cisco DevNet Associate Certification Guide

Simplifying the wording: Webhook enables the app to ( push or receive real time) . The clients Webhooks enable applications to receive real-time data by providing a mechanism for one application to send data to another as soon as an event happens. This is done through HTTP callbacks, where an event in the source system triggers an HTTP POST request to a predefined URL in the destination system. This allows the destination system to process the data immediately, ensuring real-time updates.

To minimize the security risk, storing the username and password in a vault is the best practice. A vault, such as HashiCorp Vault or AWS Secrets Manager, securely stores and manages sensitive information, providing encryption and access control. This approach ensures that credentials are not hard-coded or stored in insecure locations, reducing the risk of exposure.

A code review process involves evaluating and examining another developer's code to identify potential issues, bugs, and improvements before the code is merged into the main codebase. It helps in maintaining code quality and catching errors early in the development cycle.

Error Detection: Code reviews help detect and eliminate common mistakes and bugs that developers might overlook.

Knowledge Sharing: They promote knowledge sharing and learning among team members.

Code Quality: Ensures that the code adheres to the coding standards and best practices.

Option D is correct as the primary benefit of code reviews is to eliminate common mistakes during development.

To copy a file from one directory to another and rename it in the process, the cp (copy) command in Linux can be used with the appropriate source and destination paths:

Command Breakdown:

cp: The copy command.

./TEST/config.txt: The source file path.

./PROD/current.txt: The destination file path with the new name.

Thus, the correct command to achieve this task is: cp ./TEST/config.txt ./PROD/current.txt

References:

Linux cp Command Manual

Cisco DevNet Associate Certification Guide

In this scenario, the developer is retrieving a large number of messages from a Cisco Webex space, and the server only sends a subset of the total messages at a time. This is an example of pagination, where the data is split into multiple pages or chunks, and the client must make additional requests to retrieve the next set of data.

Pagination: This is a common API constraint used to handle large datasets by breaking them into manageable pages.

Subsequent Requests: The client needs to send subsequent requests to get the remaining data.

Option C is correct as it describes the constraint where data is divided into multiple pages and requires additional requests to retrieve all data.

Latency refers to the delay between a client request and a server response. A large distance between a client device and a host server increases the latency due to the time it takes for data to travel over the network.

Latency: The time delay experienced in a system, particularly in networking, where it refers to the time taken for data to travel from the source to the destination.

Impact: High latency can result in slow response times, negatively impacting the performance of applications, especially those requiring real-time interactions.

References:

Network Latency Overview: Network Latency

HTTP status code 429 indicates that too many requests have been sent in a given amount of time, which is a sign of rate limiting. Rate limiting is used by APIs to control the amount of incoming requests to prevent abuse or overloading the server. In this case, the Cisco Prime API is limiting the number of requests the network engineer can make in a certain time period, resulting in only a subset of devices being returned and some requests being rejected with a 429 status code.

References:

Cisco DevNet Associate Certification Guide

HTTP Status Code Definitions

Cisco Intersight is a cloud-based management platform that provides comprehensive management for Cisco UCS and HyperFlex systems. It integrates with Cisco UCS Director and UCS Manager to control server, network, storage, and virtual resources, supporting policy-driven management for up to 10,000 physical Cisco servers. Intersight offers advanced capabilities such as proactive support and a robust API for automation and integration, ensuring seamless operations across various infrastructures.

The exhibit shows that the credentials are base64 encoded and included in the source code. Base64 encoding is not a secure method of protecting credentials as it can be easily decoded. Therefore, an attacker who gains access to the source code can decode the credentials and gain unauthorized access to the account. Proper security practices should involve storing credentials securely, such as using environment variables or secure vaults, and not hardcoding them in the source code.

References:

OWASP - Storing Passwords Securely

Cisco DevNet Associate Certification Guide

The exhibit shows the router configuration for NAT (Network Address Translation). To allow traffic from the security cameras to access the Internet, the access list needs to include a permit statement for the 192.168.10.0/24 subnet.

Access List Configuration: The access list (ACL) should permit traffic from the security camera VLAN (192.168.10.0/24).

NAT Configuration: The NAT configuration uses an ACL to determine which internal IP addresses are translated to the public IP address pool.

Missing Permit Statement: Without a specific permit statement for the 192.168.10.0/24 subnet, the router does not translate the IP addresses from this subnet, resulting in a lack of Internet access for the security cameras.

References:

Cisco NAT Configuration Guide: NAT Configuration

RFC 1918 defines private IP address ranges for use within private networks. The address space 172.16.0.0 to 172.31.255.255 is designated as private and falls under class B.

Class B Address Space: The range 172.16.0.0 to 172.31.255.255 is a private IP address range designated for class B networks.

Subnet Mask: A subnet mask of 255.255.0.0 (/16) is commonly used within this range to create subnets.

References:

RFC 1918 Address Allocation: RFC 1918

The --no-ff option in the git merge command ensures that a merge commit is always created, even when a fast-forward merge is possible. This is useful for keeping a clear history of feature branches being merged into the main branch.

Fast Forward Merge: By default, Git performs a fast-forward merge if there are no diverging changes. This can result in a linear commit history without a separate merge commit.

Using --no-ff: The --no-ff option forces Git to create a merge commit, preserving the context that a feature branch was merged into the main branch, which is crucial for record-keeping and audit trails.

References:

Git Merge Documentation: Git Merge

Python classes are a fundamental aspect of object-oriented programming (OOP) in Python. They offer several benefits:

Improved Code Organization: Classes bundle data (attributes) and functionality (methods) together. This encapsulation helps keep related parts of the code together, making it easier to understand and manage.

Reusability and Inheritance: Classes support inheritance, allowing the creation of new classes based on existing ones. This promotes code reuse and can lead to a more logical structure.

Modularity: By using classes, you can create modules that encapsulate specific functionalities, making the code modular and easier to maintain.

Encapsulation and Abstraction: Classes allow for encapsulating data and functionality, providing a clear structure and abstraction layers, which enhance code readability and maintainability.

References:

Python Classes and Objects - W3Schools

Python Documentation on Classes

HTTPS (Hypertext Transfer Protocol Secure) uses port 443 by default. This port is used to secure communications over a computer network, particularly over the internet, by encrypting data between the client's browser and the web server using SSL/TLS.

References:

Cisco DevNet Documentation - Ports and Protocols

Cisco DevNet Associate Certification Guide

The PUT method is used to create or update a resource at a specific URL. In the given RESTCONF request and response example, the response indicates a successful creation of a resource, as evidenced by the HTTP status code 201 (Created). The request to create the "Australian Cattle Dog" resource under the "dogbreed" category would use the PUT method to ensure the resource is created or updated at the specified location.

References:

Cisco DevNet Documentation - RESTCONF Operations

IETF RFC 8040 - RESTCONF Protocol

HTTP status codes are divided into five classes:

1xx (Informational): Request received, continuing process

2xx (Success): The action was successfully received, understood, and accepted

3xx (Redirection): Further action must be taken to complete the request

4xx (Client Error): The request contains bad syntax or cannot be fulfilled

5xx (Server Error): The server failed to fulfill an apparently valid request

Thus, the series that relate to errors are:

400 series (Client Error)

500 series (Server Error)

References:

RFC 7231, Section 6: HTTP/1.1 Semantics and Content

The git merge-file command is used to merge changes from a specified file into the working directory file. This is particularly useful when you have a separate file with bug fixes and you need to incorporate those fixes into your production code. The command takes three files: the base file, the current file, and the file with changes. It then merges the changes into the current file.

Example usage:

bash

Copy code

git merge-file

References:

Git Documentation - git merge-file

Cisco DevNet Associate Certification Guide

To complete the requests and retrieve all the data, the correct code that needs to be added is next_url = response_json['metadata']['links']['next']. This ensures that the script retrieves the URL for the next set of data from the 'links' object within the 'metadata' section of the JSON response. This allows the loop to continue until all data is collected.

Comprehensive Detailed Step by Step Explanation with ReferencesA sandbox environment is an isolated testing environment that mimics a live network. It allows engineers and developers to run scripts and test code without affecting the production network. Cisco provides sandboxes through the DevNet portal, which are always available for testing and experimentation with network automation and programmability. Using a sandbox helps monitor the live execution of code in a controlled and safe manner, ensuring that any potential issues do not impact the actual network.

References:

Cisco DevNet Sandboxes

Cisco DevNet Associate Certification Guide

Refer to the exhibit which shows a sequence diagram illustrating a client-server interaction. The correct sequence of steps that match the code snippet is as follows:

Step 1: POST /events - The client posts an event to the server.

Step 2: GET /messages/<messageId> - The client retrieves the message details from the server using the message ID.

Step 3: Response /messages/<messageId> - The server responds with the message details.

Step 4: GET /team-memberships?teamId=<teamId> - The client retrieves team membership details using the team ID.

Step 5: POST /message - The client posts a message.

Step 6: Response /message - The server responds with the message confirmation.

The correct code snippet represents the sequence diagram correctly:

@flask_app.route('/events', methods=['POST'])

def webex_teams_webhook_events():

json_data = request.json['data']

response = requests.get(MESSAGE_URL + json_data['id'], headers=headers)

if response.json()['text'] == 'Alert':

response = requests.get(TEAM_MEMBERSHIPS_URL, headers=headers, params=params)

for info in response.json()['items']:

data = {'personId': info['personId'], 'text': 'Alert'}

The Administrative XML Layer (AXL) API in Cisco Unified Communications Manager (CUCM) allows for various administrative tasks, including the ability to authenticate users. It enables applications to interact with CUCM, retrieving user information, and authenticating users based on their credentials stored in CUCM.

To parse XML data in Python, a developer typically imports a library that provides the necessary functions and methods for XML parsing.

Libraries for XML Parsing: Python has several libraries for parsing XML, such as xml.etree.ElementTree, lxml, and minidom.

Functionality: These libraries offer functions and methods to read, manipulate, and extract data from XML files.

Example:

import xml.etree.ElementTree as ET

tree = ET.parse('file.xml')

root = tree.getroot()

References:

Python XML Parsing: Python XML Documentat

Edge computing processes data locally, close to where it is generated, rather than sending it to a centralized cloud server. This approach enhances privacy control and reduces latency.

Local Processing: Sensitive data is analyzed locally on edge devices, reducing the need to transmit potentially sensitive information over the network.

Privacy Control: By keeping data processing at the edge, organizations can better comply with data privacy regulations and reduce the risk of data breaches.

Reduced Latency: Local data processing minimizes the delay associated with sending data to and from the cloud, improving real-time analysis capabilities.

References:

Edge Computing and Data Privacy: Edge Computing Benefits

The YANG model provided in the exhibit defines the structure for interface information, including fields for name, admin-status, if-index, and statistics. The correct XML snippet must match this structure and use the appropriate namespaces and field names as defined in the YANG model.

Namespace: The XML must include the namespace urn:ietf:params:xml:ns:yang:ietf-interfaces and the prefix if.

Interface Information: The XML must include elements for name, admin-status, if-index, and statistics as defined in the YANG model.

Field Names and Values: The field names must match the YANG model (admin-status, if-index, in-octets, in-unicast-pkts).

Option D is the correct XML snippet because it accurately conforms to the YANG model. It includes the required elements and correctly uses the namespace and field names:

GigabitEthernet1

1</admin-status>

1

408164820

728061

Cisco SD-WAN (Software-Defined Wide Area Network) is a solution designed to optimize and secure connectivity across various networks. It provides several advantages including cost reduction from MPLS (Multiprotocol Label Switching), improved application performance by leveraging multiple types of connections (broadband, LTE, etc.), and simplified operations through centralized management.

Cost Reduction from MPLS: Cisco SD-WAN allows enterprises to utilize less expensive broadband internet connections alongside MPLS. This hybrid approach reduces dependency on costly MPLS circuits, significantly lowering WAN costs.

Improved Application Performance: By using application-aware routing, SD-WAN directs traffic across the best available path, ensuring better performance for critical applications.

Simplified Operations: Cisco SD-WAN centralizes network management and policy implementation, simplifying network operations and reducing the complexity associated with traditional WANs.

References:

Cisco SD-WAN Documentation: Cisco SD-WAN

Cisco Webex offers a range of collaboration capabilities, including real-time messaging, video conferencing, and integration with various productivity tools. Specifically, Webex allows users to:

Get Space History: Users can retrieve historical messages and files shared within a space, ensuring they have access to all past communications and documents.

Real-Time Notifications: Webex provides notifications when new messages are posted in spaces, allowing users to stay updated with ongoing conversations and respond promptly.

These features enhance the collaborative experience by ensuring users can keep track of conversations and receive timely updates.

References:

Cisco Webex Features

In Ansible, when using the netconf_config module to automate configuration tasks that include unique interface variables for each device, the variables should be defined in individual YAML files within the host_vars directory. This directory contains host-specific variable files named after each host, allowing Ansible to load the appropriate variables for each device during playbook execution.

References:

Ansible Documentation - Variable precedence

Cisco DevNet Associate Certification Guide

Cisco DevNet Sandbox provides developers with access to a variety of Cisco technologies in a lab environment. It is an essential resource for developers who want to test and build applications using Cisco APIs and products.

DevNet Sandbox: This platform offers pre-configured, ready-to-use environments that allow developers to experiment with Cisco products, including security products, without the need to set up and configure their own infrastructure.

References:

Cisco DevNet Sandbox

A default gateway is a router or network device that serves as an access point to another network, often the internet, when no other route is specified for a given data packet. In other words, it is used to forward traffic from the local subnet to different subnets, including external networks. When a host needs to communicate with a device on a different subnet, it sends the traffic to the default gateway, which then routes the traffic accordingly.

References:

Cisco DevNet Associate Certification Guide

Cisco Networking Essentials, Chapter on Routing and Switching Basics

The Bash script shown in the exhibit performs the following actions:

Updates the list of available packages using brew update.

Installs Docker using brew install docker.

Upgrades pip and installs tensorflow and pytorch using pip install.

Pulls the latest TensorFlow Docker image using docker pull tensorflow/tensorflow:latest.

This script is designed to install the necessary software packages (Docker, TensorFlow, PyTorch) required for a machine learning-based application. It does not create or remove any software packages but installs them.

References:

Cisco DevNet Associate Certification Guide

Docker Documentation

Homebrew Documentation

Pip Documentation

Version control systems (VCS) like Git provide numerous benefits, with one of the primary ones being the ability to track development changes. This means that every change made to the codebase is recorded along with information about who made the change, when it was made, and why. This allows teams to collaborate effectively, revert to previous versions if necessary, and understand the history of the project.

Other benefits of version control include:

Collaboration: Multiple developers can work on the same project simultaneously without overwriting each other’s work.

Branching and Merging: Developers can work on different features or bug fixes in isolation and merge their changes back into the main codebase once they are ready.

Backup: The entire history of the project is stored in the VCS, providing a backup that can be restored if necessary.

References:

Cisco DevNet Associate Certification Guide

Pro Git Book, Chapter on Getting Started

An Ethernet switch operates at the Data Link layer (Layer 2) of the OSI model. Its primary function is to forward frames between devices based on their MAC (Media Access Control) addresses. When a frame arrives at the switch, the switch reads the destination MAC address and forwards the frame to the appropriate port that connects to the device with that MAC address.

MAC Address Table: Switches maintain a MAC address table that maps each MAC address to a specific port. This table is built dynamically as the switch learns the MAC addresses of devices connected to its ports.

Frame Switching: By using the MAC address table, the switch can efficiently switch frames only to the destination port, which reduces unnecessary traffic on other ports and improves network performance.

References:

Cisco DevNet Associate Certification Guide

Cisco Ethernet Switch Operation

Telnet is a network protocol that allows a user to communicate with a remote device or server. The default TCP port used by Telnet is port 23. This port is standardized and commonly used for Telnet connections to access network devices for administrative purposes.

When using OAuth2 authentication for accessing a protected resource via a REST API, the typical flow involves obtaining an access token which can then be used to authenticate subsequent API requests. The correct process is:

POST Call to /login: Make a POST request to the /login endpoint with the user credentials (username and password) in the request body. This call will authenticate the user and, if successful, return an access token.

Use the Token: Use the retrieved token by including it in the Authorization header (usually as a Bearer token) in the request to access the protected resource, in this case, the /item endpoint.

References:

OAuth 2.0 Authorization Framework - RFC 6749

Rate limiting, as explained previously, is essential to ensure that an application can handle traffic spikes without crashing. By limiting the rate at which requests are processed, the application can maintain stability and reliability under varying load conditions.

Traffic Spike Management: Rate limiting helps manage unexpected surges in traffic by capping the number of allowable requests within a specified period.

Reliability Maintenance: By preventing overloading, rate limiting ensures that the application remains operational and responsive, maintaining its reliability.

References:

Managing Traffic Spikes with Rate Limiting: Rate Limiting Strategies