200-901 DevNet Associate (DEVASC) Questions and Answers

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

RESTCONF is a protocol used to access data defined in YANG using standard HTTP methods. However, it does not support distributed transactions, which is a requirement in this scenario.

RESTCONF: Supports YANG data models, XML encoding, and can be used in environments with software redundancy.

Distributed Transactions: RESTCONF does not support distributed transactions, which require coordination of a transaction across multiple network devices or components.

Option C is correct as the requirement for distributed transactions prevents the use of RESTCONF.

The subnet mask is used to determine the network and host portions of an IP address. It helps in defining the size of the subnet and the range of IP addresses within that subnet.

Subnet Portion: The subnet mask identifies which part of the IP address refers to the network (subnet) portion.

Host Portion: The remaining part of the IP address after applying the subnet mask identifies the specific host within the subnet.

Options A and D are correct as they capture the details about the subnet and host portions of an IP address.

Deploying applications in a public cloud provides several advantages, especially for developers dealing with temporary data processing and secure storage:

Ease in Infrastructure Management: Public cloud services offer managed infrastructure, which significantly reduces the operational burden on developers. They do not need to worry about hardware maintenance, scaling, or other infrastructure-related tasks.

Scalability: Public clouds provide scalable resources, allowing developers to adjust their infrastructure needs dynamically as per the workload requirements.

Cost-Effectiveness: Public clouds often operate on a pay-as-you-go model, which can be more cost-effective for temporary or variable workloads.

References:

Cisco DevNet Associate Certification Guide

General public cloud service provider documentation (e.g., AWS, Azure, Google Cloud)

Cisco Intersight is a platform designed to manage data center infrastructure through third-party tools and system integrations. It provides a unified management platform that integrates with Cisco UCS, HyperFlex, and other data center components, allowing for comprehensive infrastructure management, automation, and orchestration.

References:

Cisco Intersight - Overview

Cisco DevNet Associate Certification Guide

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

Rate limiting is a technique used to control the amount of incoming and outgoing traffic to or from a network. It restricts the number of API requests a user can make within a specified time window, protecting the application from being overwhelmed by too many requests at once.

Definition and Purpose: Rate limiting sets a threshold for the number of requests a user or system can make in a given timeframe (e.g., 100 requests per minute).

Implementation: Developers can implement rate limiting using various strategies such as token buckets or fixed windows.

Benefits: This constraint helps prevent abuse, reduces server load, and ensures the application remains available and performant even during high traffic periods or attacks.

References:

Rate Limiting and Throttling in APIs: Rate Limiting

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

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.

The data plane, also known as the forwarding plane, is responsible for handling the actual movement of packets through the network device, including Quality of Service (QoS). QoS involves managing and prioritizing network traffic to ensure that critical applications receive the necessary bandwidth and performance levels. The data plane processes and forwards data packets based on the policies set by the control plane.

References:

Cisco DevNet Associate Certification Guide

Cisco Networking Essentials, Chapter on Network Device Planes

Routers play a crucial role in networking by providing several key functions, including:

Broadcast Domain Segmentation: Routers separate broadcast domains, preventing broadcast traffic from one network segment from spreading to another. This improves network efficiency and reduces unnecessary traffic.

Routing: Routers forward packets between different networks based on IP addresses, enabling communication between devices on different subnets or networks.

Network Address Translation (NAT): Routers can perform NAT, which allows multiple devices on a local network to share a single public IP address.

References:

Cisco DevNet Associate Certification Guide

Cisco Router Functions

To retrieve a list of hosts using the Cisco DNA Center API, the provided Python script needs to be completed with the appropriate code snippets. Here's how the final script looks:

import json, requests, urllib3

from requests.auth import HTTPBasicAuth

from config import host, username, password

headers = { 'Content-Type': "application/json", 'x-auth-token': "csd0934rjxx" }

def dna_api_auth(host, username, password):

url = "https://{}/dna/system/api/v1/auth/token ".format(host)

response = requests.post(url, auth=HTTPBasicAuth(username, password), headers=headers, verify=False)

token = response.json()["Token"]

return token

def list_dna_devices(token):

url = "https://{}/dna/intent/api/v1/network-device ".format(host)

headers["x-auth-token"] = token

response = requests.get(url, headers=headers, verify=False)

data = response.json()

for item in data['response']:

print(item["hostname"])

token = dna_api_auth(host, username, password)

list_dna_devices(token)

application/json: This is used to set the content type for the headers.

token = response.json()["Token"]: This extracts the authentication token from the response.

data['response']: This accesses the 'response' part of the JSON data returned by the API.

token: This passes the token to the headers for authorization.

json(): This parses the response to JSON format.

for item in data['response']: This loops through each item in the response data.

hostname: This prints the hostname of each device.

References:

Cisco DNA Center Platform: Cisco DNA Center Platform

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

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

NETCONF (Network Configuration Protocol) is a standard used for network device configuration, and it utilizes YANG (Yet Another Next Generation) as a data modeling language. Cisco IOS XE and Cisco NX-OS support NETCONF and YANG to automate the configuration and management of network devices across a network. YANG defines the data models, while NETCONF provides the protocol to manipulate these models.

References:

Cisco DevNet Documentation - NETCONF and YANG

IETF RFC 6241 - NETCONF Protocol

IETF RFC 6020 - YANG Data Modeling Language

Infrastructure as Code (IaC) principles emphasize the use of code to manage and provision computing infrastructure. The key situations that align with IaC principles include:

Easily reproducible systems: Infrastructure can be recreated consistently across different environments using code, ensuring that systems are reliable and predictable.

Repeatable processes: Using scripts and configuration files to automate infrastructure setup and management ensures that processes can be repeated accurately and efficiently.

References:

Infrastructure as Code (IaC) Principles

Cisco DevNet Associate Certification Guide

Rate limiting is a technique to control the rate of incoming and outgoing traffic to or from a network. If rate limiting is not implemented, excessive API requests can overwhelm the server, causing long response times and abandoned requests.

Abandoned Requests: When a server is overwhelmed with too many requests, it may not process them all, leading to abandoned requests.

Long Response Times: Without rate limiting, the server might be handling more requests than it can efficiently process, resulting in delayed responses.

Solution: Implementing rate limiting ensures that the server processes requests at a manageable rate, improving performance and reliability.

References:

Rate Limiting and API Performance: Understanding Rate Limiting

The developer can use the Cisco DevNet API documentation to get detailed information on how to use the API for automated data collection from Webex. The API documentation includes comprehensive guides, usage examples, and authentication methods such as HTTP basic authentication. This resource helps developers understand the data formats (JSON or XML) and provides code snippets and best practices for implementation. Cisco DevNet API documentation is designed to assist developers in integrating their applications with Cisco's APIs effectively.

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

When a mobile phone using 4G fails to access the application, it is likely because the application is hosted on-premises and requires VPN connectivity to access it. On-premises applications often have network restrictions for security reasons, and access from external networks (such as 4G) typically requires a secure VPN connection to ensure data security and compliance with access policies.

The provided RESTCONF query is configuring network interfaces using the YANG data model. Based on the JSON data:

GigabitEthernet1: This interface has an enabled status set to true and an IP address configured.

GigabitEthernet2: This interface has an enabled status set to false, which means it is being shut down.

GigabitEthernet3: This interface is also set with an enabled status of false.

The descriptions for these interfaces are also included in the configuration, so the descriptions for two interfaces (GigabitEthernet1 and GigabitEthernet2) are applied.

References:

RESTCONF and YANG Model Basics

loads() function is present in python built-in 'json' module. This function is used to parse the JSON string.

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

Infrastructure as Code (IaC) applies software development practices to infrastructure management. This approach uses code to provision and manage IT infrastructure, enabling version control, automated testing, and continuous delivery.

Automated Provisioning: IaC scripts automate the setup and configuration of infrastructure resources.

Consistency: By defining infrastructure in code, environments can be consistently reproduced across different stages (development, testing, production).

Development Practices: IaC allows infrastructure to be managed with the same tools and processes as application code, including version control and automated testing.

References:

Infrastructure as Code Overview: IaC Introduction

Agile:

Optimization of the development process

Focused on the processes of a specific team

Lean:

Optimization of the production process

Focused on the processes of an organization

Agile Methodology:

Optimization of the Development Process: Agile focuses on improving and optimizing the software development process through iterative and incremental development, continuous feedback, and adapting to changes quickly.

Focused on the Processes of a Specific Team: Agile practices are typically implemented within specific development teams, emphasizing collaboration, flexibility, and team autonomy.

Lean Methodology:

Optimization of the Production Process: Lean aims to streamline the production process by eliminating waste, improving efficiency, and delivering value to the customer with the least amount of resources.

Focused on the Processes of an Organization: Lean principles can be applied across the entire organization, not just within individual teams, to improve overall processes and workflow efficiency.

References:

Cisco DevNet Associate Certification Guide, Sections on Agile and Lean methodologies

Official documentation and resources on Agile and Lean software development practices

"The Lean Startup" by Eric Ries (for Lean principles)

"Agile Software Development with Scrum" by Ken Schwaber and Mike Beedle (for Agile principles)

Therefore, the correct mapping is:

Agile:

Optimization of the development process

Focused on the processes of a specific team

Lean:

Optimization of the production process

Focused on the processes of an organization

A MAC (Media Access Control) address is a unique identifier assigned to network interfaces for communications at the data link layer of a network segment. Key features of a MAC address include:

Length and Format: A MAC address is 48 bits in length, typically represented as 12 hexadecimal digits (e.g., 00:1A:2B:3C:4D:5E).

Hexadecimal Representation: The 12 hexadecimal digits are often grouped into pairs separated by colons or hyphens for readability (e.g., 00:1A:2B:3C:4D:5E or 00-1A-2B-3C-4D-5E).

References:

IEEE 802 MAC Address Standard

Cisco MAC Address Basics

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

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 unified diff format is used to display differences between two files. The content of the file2.py file shows the added lines in the comparison.

Unified Diff Format: The format uses + to indicate lines added in file2.py and - to indicate lines removed.

Line Addition: Line 93 of file2.py has the 'DEVICE-STATS' line, as indicated by the + symbol in the diff output.

References:

Understanding Unified Diff Format: Unified Diff

The provided diff format shows changes between two versions of a file. The + signs indicate lines that have been added in the new file (new.py). The code snippet that belongs to the new file is the one with + signs, showing the addition of code to print the device list filtered by hostname. The added lines include printing the message and setting the query_string_params to filter by hostname.

The command git reset --soft HEAD^ reverses the last commit but keeps the changes staged in the index file (staging area) and working directory. Here's what the command does:

git reset --soft: Moves the HEAD pointer to the specified commit (in this case, the parent of the current commit, denoted by HEAD^) but leaves the changes from the reset commit in the staging area.

HEAD^: Refers to the parent commit of the current HEAD.

This command is useful when you want to uncommit the last commit but keep the changes for further modification or recommit them.

References:

Git Documentation - git reset

Cisco DevNet Associate Certification Guide

A 401 error indicates unauthorized access. To fix this, the script needs to include the appropriate authorization token in the request headers.

Authorization Header: The Authorization header with a Bearer token is commonly used for OAuth 2.0 authorization.

Bearer Token: This token is used to authenticate API requests securely.

Option A is correct as adding the Authorization header with the Bearer token is the proper way to authenticate the request and resolve the 401 error.

To set an environmental variable in a Linux system using Bash, the export command is used. This command sets the environment variable for the current session, and any subsequent commands or processes will inherit this environment variable.

For example, to set an environment variable named "website" with the value "cisco.com", you use the following command:

export website="cisco.com"

This sets the variable website and makes it available to any subprocesses started from the shell.

References:

GNU Bash Reference Manual - Bash Builtin Commands

Cisco DevNet Associate Certification Guide

YAML and JSON are both data serialization formats often used in configuration files. One of the key differences is that YAML supports comments, whereas JSON does not.

Comments: YAML allows comments, which makes it easier to add explanatory notes within the configuration files.

Data Representation: Both formats are used to represent data structures, but YAML is often considered more human-readable.

Option B is correct as it highlights the difference that YAML supports comments while JSON does not.

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 primary purpose of grouping devices in a VLAN (Virtual Local Area Network) is to segment a network such that devices within the same VLAN can communicate as if they are on the same physical network, regardless of their actual physical location. This allows for logical grouping of devices, providing improved network management and security.

Nonlinear development in a version control system like Git allows developers to work on different parts of the project independently and simultaneously. This approach provides several advantages:

Independent Workflows: Developers can work on different features or bug fixes without interfering with each other's work.

Parallel Development: Multiple branches enable parallel development, where teams can develop, test, and merge features separately.

Efficient Collaboration: Changes can be reviewed, tested, and merged systematically, improving collaboration among remote teams.

References:

Git and Nonlinear Development: Understanding Git Workflow

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

YANG model-driven programmability allows for the configuration of devices using data models. In NX-OS, this includes both native and OpenConfig-based models.

YANG Models: These are used to model configuration and state data for network devices. Native models are specific to the vendor, while OpenConfig models are vendor-neutral.

Configuration Management: YANG models facilitate consistent and programmable configuration of network devices, which can be done through APIs like NETCONF or RESTCONF.

Layer 2 switches use MAC (Media Access Control) addresses to direct packet transmission to the intended recipient.

MAC Address: A unique identifier assigned to network interfaces for communication on the physical network segment.

Switching: Layer 2 switches maintain a MAC address table to keep track of which MAC addresses are associated with which ports, enabling them to forward frames to the correct destination port.

There are two primary types of NAT (Network Address Translation) used in networking:

Static NAT: Maps a single private IP address to a single public IP address. This type of NAT is useful when you want a specific internal device (like a server) to be accessible from the internet using a consistent public IP address.

Dynamic NAT: Maps a private IP address to a public IP address from a pool of available public IP addresses. This type of NAT is used when you want internal devices to access the internet but do not require a consistent public IP address for each internal device.

Other types mentioned (Normal NAT, Multicast NAT, Router NAT) are not standard terms or widely recognized types of NAT.

DevOps emphasizes collaboration between development and operations teams, breaking down organizational silos to improve workflow and communication (C). Additionally, DevOps focuses on automating processes to increase efficiency, reduce manual effort, and minimize errors, often prioritizing automation over extensive documentation (E).

References:

Cisco DevNet Associate Exam Topics: DevOps Practices and Principles (understanding the core principles of DevOps)

"The Phoenix Project" by Gene Kim, Kevin Behr, and George Spafford (explains the importance of cross-functional teams and automation in DevOps)

1 – D, 2 – C, 3 – A, 4 – B

In the Bash shell, the output of a command can be redirected to a file using the > operator. This operator takes the standard output (stdout) of the command and writes it to the specified file.

Option B (devnet > output.txt): This redirects the output of the devnet command to a file named output.txt.

Option A (devnet & output.txt): This is not a valid redirection operator.

Option C (devnet < output.txt): This uses the file output.txt as input to the devnet command, which is not the requirement.

Option D (devnet I output.txt): This is not a valid redirection operator.

JSON objects are indeed collections of key-value pairs, where each key is a string, and the value can be a string, number, boolean, array, or another object. JSON is often used for data interchange due to its lightweight and readable format. Reference: JSON Introduction.

The syntax of XML includes tags, elements, and attributes. XML uses a hierarchical structure with opening and closing tags to define elements, and attributes provide additional information about elements. XML is widely used for data representation and transport. Reference: XML Basics.

JSON arrays, in contrast, are ordered collections of values (not key-value pairs), and XML objects are more complex structures with elements and attributes rather than simple key-value pairs.

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.

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.

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

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 - i, 3 - e, 4 - a, 5 - j, 6 - b, 7 - g, 8 - h, 9 - c, 10 - f

Edge computing solutions are utilized where low latency is needed. Edge computing involves processing data closer to where it is generated (at the edge of the network), which reduces the latency compared to sending data to a centralized data center for processing.

Low Latency Needs: Edge computing is designed to provide real-time data processing and decision-making by reducing the distance data has to travel. This is crucial for applications requiring immediate data processing, such as IoT devices, autonomous vehicles, and real-time analytics.

References: Cisco DevNet Associate Certification Guide, Chapter on IoT and Edge Computing.

A network interface hardware address, also known as a MAC (Media Access Control) address, is a unique identifier assigned to network interfaces for communications on the physical network segment.

Domain name: A human-readable address for network resources.

IP address: A logical address used for identifying devices on a network.

Workstation name: A human-readable name assigned to a computer.

MAC address: The correct answer, which is a hardware address assigned to a network interface.

Solution as below

When using Basic Authentication in HTTP, the username and password are concatenated with a colon (:) in between. This concatenated string is then encoded using Base64. For the provided username devnet and password Cisco123, the string devnet:Cisco123 is encoded in Base64, resulting in ZGV2bmV0OkNpc2NvMTIz. This Base64 string is then included in the HTTP Authorization header. This process is described in the RFC 7617 and is a standard practice in HTTP Basic Authentication.

A version control system offers several advantages:

Branching and Merging: Developers can work on features, bug fixes, or experiments in isolation (branches) without affecting the main codebase. Once the work is completed, it can be merged back into the main branch, facilitating organized and controlled development workflows.

Edge computing is a distributed computing paradigm that brings computation and data storage closer to the sources of data. This helps to:

Reduce Latency: By processing data closer to where it is generated, edge computing reduces the time taken for data to travel to a central server and back. This is especially important for applications requiring real-time or near-real-time responses.

Optimize Bandwidth: Reducing the amount of data sent to a central data center can conserve bandwidth and lower costs.

Enhance Security and Privacy: Processing data locally can enhance security and privacy by minimizing the exposure of data during transmission.

This Python script uses the Cisco DNA Center API to retrieve a list of network devices. The steps are:

Import the required libraries: requests for making HTTP requests and json for handling JSON data.

Define the API endpoint URL for retrieving network devices from Cisco DNA Center.

Set up the request headers, including the content type and the authentication token (X-Auth-Token).

Send a GET request to the API endpoint.

Check the response status code to ensure the request was successful.

If successful, parse and print the JSON response containing the list of network devices. Otherwise, print an error message.

When a developer is writing an application that interacts with a REST API, the status code of the response is a critical element used in conditional checks. The status code provides information about the success or failure of the request. Common status codes include:

200: OK (The request was successful).

201: Created (The resource was successfully created).

400: Bad Request (The server could not understand the request due to invalid syntax).

401: Unauthorized (Authentication is required and has failed or has not been provided).

404: Not Found (The requested resource could not be found).

By checking the status code, the application can determine if the request was successful and handle errors appropriately.

The script provided in the exhibit shows the following steps:

It configures a loopback interface (interface loopback 5; no shut).

It retrieves the interface details and parses the JSON output to list interfaces that are up.

Therefore, the correct answers are: A. Configure interface loopback 5. C. Show only the interfaces in the up status.

Generating log bundles is a resource-intensive task that can cause high CPU utilization on the Cisco DNA Center. When the CPU spikes, it can affect the performance of other critical tasks, such as forwarding voice IP packets, leading to delays and poor voice quality. This is especially noticeable during business hours when network utilization is high, and voice traffic is sensitive to latency and jitter. More details can be found in Cisco DNA Center documentation on Managing Logs and System Performance.

Artifact repositories play a crucial role in Continuous Integration/Continuous Deployment (CI/CD) pipelines by:

Storing Build Artifacts: They store files needed during the build process, such as dependencies, and files generated during the build process, such as binaries.

Providing Traceability: They offer traceability and versioning of binary files, which is essential for managing builds and releases.

Search and Management: They allow developers to search and manage binary files efficiently, ensuring that the correct versions of dependencies are used.

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

Infrastructure as Code (IaC) involves managing and provisioning computing infrastructure through machine-readable definition files, rather than physical hardware configuration or interactive configuration tools.

Principles of IaC:

Reusability: Complete complex systems must be built from reusable infrastructure definitions. This means infrastructure components should be modular and reusable across different environments and applications.

Consistency: Environments must be provisioned consistently using the same inputs. This ensures that every environment is set up exactly the same way, reducing the risk of errors and discrepancies.

Other Principles:

Declarative Configuration: Using a high-level language to define what the infrastructure should look like rather than how to achieve it.

Version Control: Infrastructure definitions are stored in version control systems, making changes trackable and reversible.

Incorrect Options:

C. Redeployments cause varying environment definitions: This is against IaC principles as it emphasizes consistency.

D. Service overlap is encouraged to cater for unique environment needs: This could lead to complex and unmanageable configurations.

E. Components are coupled, and definitions must be deployed for the environment to function: IaC promotes decoupled, modular components.

References:

Infrastructure as Code: IaC Principles

Code review is typically performed before the merge of code in a version control system. This process involves examining code changes to ensure they meet the required standards, are free of bugs, and align with the project’s goals. The review usually happens after code has been committed to a feature branch but before it is merged into the main branch. This helps maintain the integrity of the main branch and ensures that any issues are caught early. More information can be found in best practices for code review.

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.

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

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)

========================

A hybrid cloud solution is best suited for a company that wants to use on-premise infrastructure while also leveraging user self-service and scalability features of the cloud.

Hybrid Cloud:

Definition: A hybrid cloud combines on-premise infrastructure (private cloud) with public cloud services, allowing data and applications to be shared between them.

Scalability: Hybrid cloud allows for the flexibility to scale resources up or down as needed. When demand exceeds the capacity of the on-premise infrastructure, additional resources from the public cloud can be utilized.

Self-Service: Users can provision and manage resources without IT intervention, typically through a self-service portal.

Use Cases: This is ideal for businesses that need to maintain control over certain data and applications while taking advantage of the scalability and cost-efficiency of the public cloud.

Other Cloud Types:

Public Cloud: Fully managed by third-party providers and shared among multiple organizations. It offers high scalability but may have concerns about data privacy and control.

Private Cloud: Exclusively used by one organization, providing more control and security but may be limited in scalability compared to public cloud.

Multi-Cloud: Use of multiple cloud services from different providers, which can be complex to manage but provides flexibility and redundancy.

References:

Cisco Cloud Solutions: Hybrid Cloud Solutions

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.

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

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.

1 – B, 2 – E, 3 - F

Cisco DNA Center is a network management and command center for enterprise networks, providing network controller-level management features. It offers capabilities such as automation, assurance, fabric provisioning, and policy-based segmentation, making it a comprehensive solution for managing and optimizing network performance and operations. Cisco DNA Center is part of the broader Cisco Digital Network Architecture (Cisco DNA), designed to facilitate the efficient and automated management of networks. More information can be found on the Cisco DNA Center product page.

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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.

A router is a network device that routes traffic between different broadcast domains and subnets. Routers operate at the network layer (Layer 3) of the OSI model and use IP addresses to make forwarding decisions. They are responsible for determining the best path for data packets to travel across interconnected networks, ensuring that traffic is correctly directed from one broadcast domain to another.

References:

Cisco Router Basics

Broadcast Domains and Routers

=========================

The Model-View-Controller (MVC) design pattern is a software architectural pattern that separates an application into three main logical components: the Model, the View, and the Controller. Each of these components is built to handle specific development aspects of an application.

Advantages of MVC:

Allows for multiple views of the same model (Option B):

In the MVC architecture, the Model component represents the data and the business logic of the application. It is independent of the user interface. This separation allows the application to have multiple views that can present data in different ways without requiring changes to the underlying data model. For example, the same data can be displayed in a web application, a mobile app, or even a command-line interface, all using the same model.

Separates responsibilities of the code, which makes future modifications easier (Option E):

By separating the application into distinct components (Model, View, Controller), MVC clearly defines the responsibilities of each part. The Model is responsible for data management, the View for the user interface, and the Controller for handling user input and interactions. This separation of concerns makes the application easier to maintain and modify. Future changes can be made to one component without significantly affecting the others. For instance, changes to the user interface can be made in the View without altering the underlying data model or the business logic in the Model.

Other Considerations:

Simplifies network automation (Option A): While MVC can be used to create applications that interact with network automation tools, simplifying network automation is not a direct advantage of the MVC pattern itself.

Makes code easier to deploy using CI/CD pipelines (Option C): CI/CD pipelines benefit from modular and well-structured code, but the MVC pattern specifically addresses the organization of code and separation of concerns, rather than deployment processes.

Reduces need for error handling (Option D): Error handling is an essential aspect of any application and is not inherently reduced by the use of MVC. Instead, MVC helps in organizing the code in a way that might make error handling more systematic, but it does not directly reduce the need for it.

The separation of concerns and the ability to have multiple views of the same model are core advantages of using the MVC pattern, making it a powerful design approach for creating scalable and maintainable applications.

References:

Model-View-Controller (MVC) Architecture

Cisco DevNet Developer Resources

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

The exhibit demonstrates an example of cross-site scripting (XSS). This type of attack involves injecting malicious scripts into web pages viewed by other users. In this example, the script <script>alert('I want to pass the DevNet Associate Exam.');</script> is embedded into a URL, and when accessed, it displays an alert message in the web browser.

Cross-Site Scripting (XSS): A security vulnerability typically found in web applications that allows attackers to inject malicious scripts into content from otherwise trusted websites.

References: Cisco DevNet Associate Certification Guide, Chapter on Security, and OWASP documentation on Cross-Site Scripting.

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

Load balancers distribute network or application traffic across multiple servers to ensure no single server becomes overwhelmed. In modern application deployment, load balancers allow traffic to continue smoothly as new compute units are brought online and old units are decommissioned. This ensures high availability and reliability of services.

The Dockerfile shown in the exhibit sets up an NGINX container with a delay before starting the NGINX service. It uses the ENTRYPOINT and CMD directives to define the commands that should be executed when the container starts.

ARG and ENV: These lines define and set an argument and environment variable for the delay.

ENTRYPOINT: Specifies the executable to run, in this case, /bin/sh.

CMD: Provides additional arguments to the ENTRYPOINT, which are -c and the command string to execute.

The combined command that will be executed is: /bin/sh -c "/bin/sleep 30 && nginx -g 'daemon off;'"

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

In test-driven development (TDD), the "green bar" refers to the visual indication that all tests have passed, typically seen in a testing framework. Two of the patterns that developers use to reach the green bar in TDD are "triangulate" and "fake it."

A. another test - This is not a green bar pattern; it's a step in the TDD cycle but not a pattern for passing tests. B. break - This is not a TDD pattern. C. triangulate - Correct. Triangulation involves adding another test to force the implementation to be more generic and robust. D. starter test - This is not a TDD pattern. E. fake it - Correct. Faking it means to return a simple, hard-coded value to make the test pass.

References:

Test-Driven Development (TDD) Patterns

Growing Object-Oriented Software, Guided by Tests

Webhooks are user-defined HTTP callbacks triggered by specific events. They are effective in scenarios where an automated response to an event is required. For example, informing a chat channel after a deployment event or sending an email after a transaction are practical uses of webhooks. These use cases leverage the real-time capabilities of webhooks to automate responses and notifications based on events.

References:

Cisco DevNet Associate Study Guide: Event-Driven Automation (Chapter 8, Section: Webhooks and Their Use Cases).

In the provided Python function enable_function, the parameters are if_name, if_status, and if_type, which correspond to the interface name, status (enabled/disabled), and interface type respectively.

Function Parameters: The function enable_function is designed to take three parameters: the interface name (if_name), the status (if_status), and the type (if_type).

Correct Order and Values: To enable the interface named "Loopback1", you need to pass the correct values in the order they are defined in the function.

Option A correctly calls the function with the interface name "Loopback1", the status true (enabled), and the interface type 'iana-if-type:softwareLoopback'.

For applications with significant disk I/O requirements, deploying directly on bare metal (physical servers) can provide the best performance and meet specific platform requirements.

Disk I/O Performance: Bare metal servers offer direct access to hardware resources, ensuring maximum disk I/O performance.

Automation: Modern infrastructure automation tools can fully automate the deployment, configuration, and management of bare metal servers.

Option C meets the requirements of significant disk I/O performance and full automation.

To create a running container based on a tagged Docker image with the container port 8080 bound to port 80 on the host, you use the docker run command with the -p flag.

A. docker build -p 8080:80 alpine

- Incorrect. docker build is used to build an image, not run a container. B. docker exec -p 8080:80 alpine

- Incorrect. docker exec is used to run a command in a running container. C. docker start -p 8080:80 alpine

- Incorrect. docker start starts a stopped container but does not create one. D. docker run -p 8080:80 alpine

- Correct. This command runs a new container from the image and maps the ports.

References:

Docker Run Command

In the provided sequence diagram, each call must complete before the next one can proceed, indicating that the calls are synchronous. Synchronous calls block further execution until the response is received, maintaining a sequential order of operations.

Synchronous Nature: The diagram shows each function call being made and then waiting for a callback before proceeding to the next step.

Blocking Behavior: Each interaction completes fully before the next one starts, which is characteristic of synchronous operations.

Option C correctly identifies that all the calls shown in the sequence diagram are synchronous.

The error code 401 indicates an unauthorized request, which can often result from using an incorrect API endpoint. To solve this problem, ensure that the API URL correctly matches the endpoint for retrieving the device list. This URL must point to the correct API endpoint as specified by the Cisco DNA Center API documentation.

References:

Cisco DevNet Associate Study Guide: Interacting with Cisco DNA Center APIs (Chapter 7, Section: Using API Endpoints and Proper Authentication).

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.

The 401 Unauthorized status code indicates that the request lacks valid authentication credentials. When using OAuth2 for authenticating with the Cisco Webex API, the correct approach is to include a Bearer token in the Authorization header.

header = {"Authorization": "Bearer YOUR_TOKEN"}

This option correctly formats the Authorization header, which is necessary for the Webex API to authenticate the request. The Bearer token is a type of token used by OAuth2 to access protected resources.

Authorization Header: The header must contain the key "Authorization" with the value formatted as "Bearer YOUR_TOKEN".

Bearer Token: The Bearer keyword followed by a space and the token itself is the correct way to pass the OAuth2 token in the header.

Option B:

Incorrect because it uses "Authentication" instead of "Authorization".

Option C:

Incorrect because it combines Authentication and Bearer incorrectly without a space.

Option D:

Incorrect for the same reason as Option C.

References:

Cisco Webex API Authentication

OAuth2 Authorization Header =====================

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 sequence diagram shows the process where the API client first calls the /organizations endpoint to get the list of organization IDs. Then, for each organization, it makes a call to the /organizations/(orgId)/networks endpoint to retrieve the networks for that organization. Since there are two organizations, the GetAllNetworks function will make two parallel calls to the /organizations/(orgId)/networks endpoint, one for each organization.

References:

Cisco DevNet Associate Study Guide: Using Cisco Meraki APIs (Chapter 7, Section: Understanding Meraki API Calls and Endpoints).

Edge computing involves processing data closer to where it is generated (the "edge" of the network) rather than sending it to a centralized data center or cloud for processing. This approach reduces latency and bandwidth usage, providing high-speed data processing capabilities. It is particularly beneficial for IoT implementations where real-time processing and response are crucial.

References:

Cisco DevNet Associate Study Guide: IoT and Edge Computing (Chapter 9, Section: Benefits of Edge Computing).

The exhibit shows a unified diff output, which indicates changes made to files in a version control system (e.g., git). The files being edited are indicated by the diff --git lines.

Identifying Files: The diff output shows changes to two files:

ciscoaxl/axl.py: Indicated by the line diff --git a/ciscoaxl/axl.py b/ciscoaxl/axl.py.

setup.py: Indicated by the line diff --git a/setup.py b/setup.py.

Unified Diff Format: The format includes the file paths, lines added (+), and lines removed (-).

Options B and D are the correct answers as they correspond to the files setup.py and ciscoaxl/axl.py.

A model-driven approach for infrastructure automation offers several benefits. One of the primary advantages is that it provides a small learning curve and helps system administrators with limited coding experience. By using high-level models and declarative languages, administrators can define the desired state of the infrastructure without needing to write complex scripts.

Declarative Language: Model-driven approaches use declarative languages that allow users to specify what the desired state should be, rather than how to achieve that state. This abstracts the complexity of the underlying automation processes.

References: Cisco DevNet Associate Certification Guide, Chapter on Infrastructure as Code and Model-Driven Programmability.

When an application interacts with a webhook, it is typically characterized as a "listener" or "receiver." A webhook is a way for an application to provide real-time data to other applications as events occur. The listener or receiver application waits for incoming HTTP requests (events) triggered by certain activities on another application, making it possible to process the data immediately upon receipt.

References:

Cisco DevNet Associate Study Guide: Event-Driven Programming (Chapter 8, Section: Understanding Webhooks and Their Applications).

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).

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.

Using functions in code improves the development process by enabling faster code development. Functions help modularize the code, making it easier to manage, reuse, and debug, which speeds up the development process.

A. better user experience in the end product - Incorrect. This is not directly related to the use of functions in code. B. improves code performance - Incorrect. While functions can sometimes improve performance, the primary benefit is modularity and reuse. C. easier to compile the code - Incorrect. Functions do not inherently make the code easier to compile. D. faster code development - Correct. Functions make development faster by allowing code reuse and simplifying debugging.

References:

Cisco Programming Fundamentals

The agile process allows for incremental delivery of features, meaning new functionalities can be added or existing ones updated in small, manageable increments. This is in contrast to the waterfall model, where all phases are completed before the product is delivered. Agile enables continuous improvement and adaptation to changing requirements throughout the development process.

To create and switch to a new branch called "my-bug-fix" in Git, you use the git checkout -b command. This command creates the branch and switches to it in one step.

A. git checkout -b my-bug-fix - Correct. This command creates a new branch and switches to it. B. git branch -b my-bug-fix - Incorrect. The -b option is not valid with git branch. C. git branch my-bug-fix - This creates a new branch but does not switch to it. D. git checkout my-bug-fix - This switches to an existing branch but does not create a new one.

References:

Git Branching - Creating a Branch

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).

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 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.

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.

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.

Cisco Umbrella provides cloud-delivered security that includes malware and content filtering through DNS. It is designed to block malicious domains, IP addresses, and URLs before they can reach your network or endpoints.

DNS-Layer Security: Cisco Umbrella uses DNS to prevent connections to known malicious sites by blocking the DNS request, thereby preventing the initiation of malicious connections.

Content Filtering: It also provides content filtering to block inappropriate or non-business-related websites based on customizable policies.

Option D is the correct answer because Cisco Umbrella is specifically known for its DNS-layer security capabilities, including malware and content filtering.

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

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.

The bash script shown in the exhibit automates the process of downloading, extracting, compiling, installing, and configuring the Cisco DevNet application. It also enables and starts the application automatically.

Download and Extract: The script uses curl to download a tar.gz file and then extracts it using tar -zxf.

Compilation and Installation: The ./configure && make && make install commands compile and install the application.

Enabling and Starting the Service: The systemctl enable devnet and systemctl start devnet commands ensure the application starts automatically on system boot and starts it immediately.

Option B correctly describes the workflow as it includes compilation, installation, configuration, and automatic startup of the application.

The Bash script performs the following steps within the loop:

Reads each line from sites.txt.

Copies template.conf to a new file in the /etc/nginx/sites-available directory for each site.

Creates a symbolic link to the new file in the /etc/nginx/sites-enabled directory.

Changes the ownership of the new files to www-data.

This process creates a configuration file for each site, creates a link to enable the site, and ensures the correct permissions.

The Waterfall method is a sequential software development process where a phase begins only after the previous phase has ended. In contrast, Agile development involves iterative processes where phases run in parallel and are continuously improved upon.

A. Waterfall increases agility to implement faster while Agile promotes reliability - Incorrect. This is the opposite of the typical characteristics of these methods. B. A phase begins after the previous phase has ended in Waterfall while Agile phases run in parallel - Correct. Waterfall is linear and sequential, while Agile is iterative and parallel. C. Customers get feedback during the process in Waterfall while they can see the result at the end in Agile - Incorrect. Agile involves continuous feedback, whereas Waterfall typically provides feedback only at the end. D. Requirements can be updated in Waterfall while in Agile it should be gathered in the beginning - Incorrect. Requirements in Agile can be updated continuously, while Waterfall requires requirements to be defined upfront.

References:

Waterfall vs. Agile Methodologies

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

NETCONF (Network Configuration Protocol) allows for the exchange of configuration data and state information between a network device and a management system using XML-encoded messages over a secure SSH connection.

A. allows Python scripts to be executed externally from a network device - Incorrect. This is not a capability of NETCONF. B. uses JSON to encode data in its content layer - Incorrect. NETCONF uses XML for encoding data. C. allows XML messages to be exchanged via the SSH protocol - Correct. NETCONF uses XML to encode configuration data and state information, and it uses SSH as the transport protocol. D. exposes a web-based interface - Incorrect. NETCONF itself does not provide a web-based interface; it operates over SSH.

References:

NETCONF Protocol

A MAC address (Media Access Control address) is a unique hardware address assigned to the network interface of a device. It is used for network communication at the data link layer of the OSI model.

A. unique network address that identifies the network interface of a device - Incorrect. This describes an IP address. B. unique network interface address that is provided by the DHCP server - Incorrect. MAC addresses are hardware-based, not provided by DHCP. C. unique hardware address that identifies the network interface of a device - Correct. This is the correct definition of a MAC address. D. unique hardware interface address that is provided by the central switch - Incorrect. MAC addresses are not provided by switches.

References:

Cisco MAC Address Basics

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.

The docker build command is used to build an image from a Dockerfile. The -t option tags the image with a specified name and tag.

Tagging: The docker tag command associates an image ID with a repository and tag.

Building with Tag: The correct command to build the Docker image and tag it as local/app:0.4 is docker build -t local/app:0.4.

Option D is the correct command to build and tag the image.

A load balancer distributes incoming network traffic across multiple servers to ensure that no single server bears too much load. This helps in balancing the traffic load, improving performance, and enhancing the availability of the applications hosted on the servers.