200-901 Practice Questions

Cisco DNA Center (now Cisco Catalyst Center) utilizes a RESTful API architecture for network management. To retrieve information from the controller, such as a list of inventory, the standard HTTP GET method is employed. The specific endpoint https://<address>/api/v1/network-device/ is designed to query the inventory database and return a collection of device objects. In alignment with modern web standards and Cisco’s Northbound API design, the response payload is delivered in JSON (JavaScript Object Notation) format, which allows for easy parsing by automation scripts and management applications.

Cisco DevNet Documentation: Cisco DNA Center Intent API Reference Guide (v2.x). Section: "Know Your Network - Get Device List". URL: https://developer.cisco.com/docs/dna-center/

Cisco Press: CCNP and CCIE Enterprise Core ENCOR 350-401 Official Cert Guide. Chapter 25: "Fabric Technologies and Network Design", Section: "Cisco DNA Center REST API".

Cisco Systems, Inc.: Cisco DNA Center Platform Configuration Guide, Release 2.3.3. "Working with Intent APIs - GET Method Operations", Paragraph 4.2.

University Courseware: Stanford CS144: Introduction to Computer Networking. Module: "Application Layer Protocols - REST and JSON in Network Controllers".

The primary goal of a Continuous Integration/Continuous Delivery (CI/CD) pipeline is to automate the software delivery process. The core principle is to minimize manual interaction from code commit to deployment. By automating the build, integration, testing, and deployment stages, CI/CD reduces the risk of human error, increases the speed and frequency of releases, and provides rapid feedback to developers. This high degree of automation is fundamental to achieving the reliability and efficiency promised by DevOps practices.

A. A key objective of CI/CD is to automate testing as much as possible to ensure speed and consistency, not to rely on manual testing.

C. CI/CD enables frequent, on-demand deployments, directly opposing the idea of a rigid, infrequent (e.g., monthly) release schedule.

D. While providing feedback is a critical function of the pipeline, it is a means to an end. The overarching goal is the automation itself, which enables this rapid feedback.

1. Official Vendor Documentation:

Cisco DevNet, "Introduction to CI/CD," Section: "What is CI/CD?". The documentation states, "The main goal of CI/CD is to make the application/service development and release process faster and more robust by using an automated pipeline." This emphasizes automation as the core mechanism.

2. University Courseware:

University of California, Berkeley. CS 169A, "Software Engineering," Lecture 10: "Continuous Integration & Delivery/Deployment." The lecture notes emphasize that a primary goal is to "Automate the build, test, and deployment process" to ensure that every check-in is verified and can be released, thus minimizing manual steps.

3. Peer-reviewed Academic Publication:

Shahin, M., Ali, A., Babar, M. A., & Zhu, L. (2017). "Continuous Integration, Delivery and Deployment: A Systematic Review on Approaches, Tools, Challenges and Research Directions." IEEE Access, 5, 3909-3943. In Section III-A, "Definitions of CI, CD, and DevOps," the authors define the practices based on the principle of automating the software delivery lifecycle to reduce manual effort and enable frequent releases. (DOI: https://doi.org/10.1109/ACCESS.2017.2685629)

To add modified local files to a remote repository, a specific three-step sequence is required:

1. git add .: This command adds all modified and new files in the current directory to the Staging Area (index), preparing them for the next commit.
2. git commit -m "...": This records the staged changes to the Local Repository (HEAD) with a descriptive message, creating a new snapshot in the project history.
3. git push: This uploads the local repository commits to the Remote Repository, making the changes available to other collaborators.

git pull is used to fetch and merge remote changes to local, and git checkout -b is used for branch management; neither is used to upload local modifications.

Microsoft Learn (Dynamics 365 Business Central): "Use Git for AL Development" - Section on Committing and pushing changes.

Pro Git Book (Chacon & Straub): Section 2.2 Git Basics - Recording Changes to the Repository. [Online Version via Git-SCM].

GitHub Docs: Managing files on GitHub -> "Adding a file to a repository using the command line".

Atlassian Git Tutorials: Saving Changes -> "git add", "git commit", and "git push" workflows.

Version Control Software (VCS), such as Git, is fundamental for modern software development and network automation. Its primary advantages are centered on managing changes to source code over time. A core feature is the ability to compare different versions or revisions of text-based files, allowing developers to see specific changes (additions, deletions, modifications) between commits. This is crucial for code reviews and debugging. Additionally, VCS provides a complete, centralized history of the project, which enables new team members to quickly get up to speed by accessing the latest code and understanding its evolution.

A. While VCS can store binary files, it cannot effectively compare or "diff" them to show changes, which is a known limitation, not an advantage.

B. Hosting packaged applications is the function of an artifact repository (e.g., Artifactory, Nexus), not a primary advantage of a version control system.

C. Wiki software is a feature of platforms that host VCS repositories (like GitHub or GitLab), not an inherent feature of the version control software itself (like Git).

1. Chacon, S., & Straub, B. (2014). Pro Git (2nd ed.). Apress.

Chapter 1.1, About Version Control: "With a VCS, you can: ...compare changes over time... This also means that if you screw things up or lose files, you can generally recover easily." This directly supports option D. The chapter also discusses collaboration, stating, "It also helps your team work together," which aligns with the benefit described in option E.

2. MIT. (2020). The Missing Semester of Your CS Education. MIT Courseware.

Lecture 6: Version Control (Git), "Why use a version control system?": The course notes state, "VCS lets you: see the entire history of changes... see who wrote what line of code and when ('git blame')." This supports option E, as it facilitates onboarding and team collaboration by providing access to the project's full history. The lecture also extensively covers the git diff command, which is the mechanism for comparing revisions, supporting option D.

3. Cisco. (2020). Cisco Certified DevNet Associate DEVASC 200-901 Official Cert Guide. Cisco Press.

Chapter 21, "Using Git for Version Control": This chapter explains that a key benefit of Git is its ability to track changes and allow developers to see the difference between versions. It states, "Git allows you to see the history of changes to a file... You can also compare any two versions of a file." This directly validates option D. The chapter also emphasizes collaboration, noting that Git enables teams to work on the same codebase, which supports the principle in option E.

Control Plane: This plane is responsible for "learning" the network topology and building the forwarding tables. It processes traffic destined to the router itself to maintain connectivity. BGP is a routing protocol used to exchange reachability information, and signaling protocols (like RSVP or LDP) establish paths; both are core control plane functions.

Management Plane: This plane is dedicated to the administration of the device. It handles protocols used for monitoring and configuration. NETCONF is a network management protocol, and any configuration change protocols fall into this category as they define how the device is managed rather than how traffic is routed.

Data Plane (Forwarding Plane): This plane handles the actual movement of user packets. It uses the logic provided by the control plane to perform hardware forwarding decisions at high speeds and manages transit traffic—traffic that enters one interface and exits another without being processed by the local CPU.

RFC 7426 (Software-Defined Networking: Layers and Terminology): Sections 3.1 (Control Plane) and 3.2 (Management Plane) define the functional separation between protocol learning and device configuration. https://datatracker.ietf.org/doc/html/rfc7426

Cisco Systems - "Control Plane, Data Plane and Management Plane": This documentation specifies that BGP and routing protocols reside in the Control Plane, while NETCONF and SSH reside in the Management Plane. (Doc ID: 116117).

Juniper Networks - "Day One: Finishing Junos Strategy": Page 14-16 describes the separation of the Routing Engine (Control/Management) from the Packet Forwarding Engine (Data Plane), specifically identifying transit traffic as a Data Plane function.

Stanford University (CS144: Introduction to Computer Networking): Course modules on "The Data Plane" and "The Control Plane" detail how hardware-based forwarding (Data Plane) differs from software-based path computation (Control Plane).

To enable and verify the keepalive setting for FastEthernet 2/0, the script must follow these logical steps:

1. Instantiation: Based on the documentation exhibit, the class is Native.Interface.FastEthernet. We must instantiate this specific class to access its attributes.
2. Configuration: The exhibit shows keepalive is a boolean attribute of the FastEthernet class. Setting interface.keepalive = True prepares the local object. (Note: interface.name = '2/0' is already provided in the code).
3. Operation: To satisfy the final if interface_data: logic, we must populate interface_data. Since the goal is to check if keepalive is enabled (likely after a configuration push or to verify current state), crud.read is used to fetch the operational data from the device into the interface_data variable.

Cisco DevNet Documentation: YDK-Py Getting Started. This guide details the CRUD (Create, Read, Update, Delete) service and how crud.read(provider, filter) is used to retrieve data from a network device using a model-driven approach.

Cisco IOS XE YANG Model Reference (GitHub: CiscoDevNet/yang). The Cisco-IOS-XE-native.yang model defines the hierarchy where native/interface/FastEthernet exists. The Python YDK library maps these YANG containers directly to Python classes.

YDK-Py API Reference (FastEthernet Class): Documentation for the ydk.models.cisco_ios_xe.Cisco_IOS_XE_native module specifies that the FastEthernet class contains the name (key) and keepalive (boolean) leaves as direct attributes.

Cisco Live Documentation (DEVNET-2011): "Model-Driven Programmability with YANG, NETCONF, and YDK" explains the lifecycle of a YDK object: Instantiate -> Set Attributes -> Invoke CRUD Service.

According to the Docker documentation, each instruction in a Dockerfile serves a specific role in image creation. The FROM instruction initializes a new build stage and sets the Base Image; it must be the first instruction. VOLUME creates a mount point for externally mounted volumes or persistent data. ENTRYPOINT allows you to configure a container that will run as an executable, meaning it will start with a specific command that cannot be easily overridden. EXPOSE functions as documentation between the image developer and the person running the container, informing Docker that the container listens on specific network ports at runtime. The RUN instruction (not used here) executes commands in a new layer.

Docker Official Documentation: "Dockerfile reference - FROM". Accessed 2025. [https://docs.docker.com/engine/reference/builder/#from]

Docker Official Documentation: "Dockerfile reference - VOLUME". Accessed 2025. [https://docs.docker.com/engine/reference/builder/#volume]

Docker Official Documentation: "Dockerfile reference - ENTRYPOINT". Accessed 2025. [https://docs.docker.com/engine/reference/builder/#entrypoint]

Docker Official Documentation: "Dockerfile reference - EXPOSE". Accessed 2025. [https://docs.docker.com/engine/reference/builder/#expose]

University of Helsinki: "DevOps with Docker" course materials, Part 1: Dockerfile instructions. [https://devopswithdocker.com/]

The control plane is the logical component of a network device responsible for making forwarding decisions. It handles all signaling and protocol traffic used to discover the network topology and build forwarding tables. This includes running routing protocols like OSPF, EIGRP, and BGP to exchange routing information with other devices. The control plane processes this information to create the routing table and then programs the data plane (e.g., by creating the FIB) to handle the actual packet forwarding.

A. The data plane is responsible for the high-speed forwarding of user traffic based on the instructions provided by the control plane.

B. The management plane is used for administrative access and device management, handling protocols like SSH, Telnet, and SNMP.

C. The authentication plane is not a standard, distinct plane in network architecture; authentication is a function often handled within the management or control planes.

1. Cisco Systems, Inc., "Control Plane Policing Implementation Guide, Cisco IOS XE Release 3S". Cisco Technology & Support Documentation. In the "Control Plane Policing Overview" section, it states, "The control plane is responsible for routing and for handling traffic that is directed to the router. This traffic includes routing protocol packets..."

2. Cisco Systems, Inc., "The Cisco ASR 9000 Series Aggregation Services Router Control Plane". Cisco White Paper. Section: "Control Plane and Data Plane", Paragraph 1. "The control plane’s main function is to provide the intelligence to run the network. It supports all signaling and routing protocols that are required to build and maintain the routing and forwarding tables..."

3. Feamster, N., Rexford, J., & Zegura, E. (2014). "The Road to SDN: An Intellectual History of Programmable Networks". ACM SIGCOMM Computer Communication Review, 44(2), 87–98. https://doi.org/10.1145/2602204.2602219. In Section 2, "The Data, Control, and Management Planes," the paper defines the control plane as the component that "computes the forwarding table used by the data plane," explicitly including routing protocols in its function.

The Network Time Protocol (NTP) is an application layer protocol used for synchronizing the clocks of computer systems over a network. NTP is designed to be lightweight and efficient, using the User Datagram Protocol (UDP) as its transport layer protocol. Specifically, NTP client-server communication occurs over UDP port 123. Because UDP is connectionless and has lower overhead than TCP, it is suitable for the periodic, small query-response exchanges typical of NTP. For NTP services to function correctly across a firewall, the firewall rules must be configured to permit UDP traffic on port 123.

A. ICMP is a network layer protocol used for diagnostics and error reporting (e.g., ping), not for transporting application data like time information.

B. BGP is an application layer routing protocol used to exchange routing information between autonomous systems; it uses TCP, not UDP, and is unrelated to time synchronization.

D. TCP is a connection-oriented transport protocol that provides reliable delivery. NTP is specifically designed to use the connectionless UDP for its operations.

1. IETF RFC 5905: Mills, D., Martin, J., Burbank, J., & Kasch, W. (2010). Network Time Protocol Version 4: Protocol and Algorithms Specification. RFC 5905. The abstract explicitly states, "It is built on the User Datagram Protocol (UDP), which in turn runs on the Internet Protocol (IP)."

2. Cisco Press: Odom, W. (2019). CCNA 200-301 Official Cert Guide, Volume 1. Cisco Press. Chapter 2, "Fundamentals of TCP/IP Transport and Applications," lists well-known TCP and UDP ports, identifying NTP as using UDP port 123.

3. University Courseware: Kurose, J. F., & Ross, K. W. (2021). Computer Networking: A Top-Down Approach (8th ed.). Pearson. In Section 2.7, "Socket Programming: Creating Network Applications," the textbook's appendix on well-known ports lists NTP as an application layer protocol that uses UDP port 123. This text is standard courseware in numerous university computer science programs.

A routing table is a data file in a router that lists the routes to particular network destinations. Its primary purpose is to help the router make forwarding decisions. For any given destination IP address, the router performs a lookup in its routing table to find the best match. The corresponding entry provides the essential information on how to forward the packet, which is either the IP address of the next-hop router or the specific outgoing interface on the local router that leads toward the destination.

A. IP protocol: The IP protocol field (e.g., TCP, UDP, ICMP) is Layer 3 information but is not a column in a standard routing table used for destination-based forwarding.

B. Broadcast address: A broadcast address is a type of destination address, not a component or field within a routing table entry that defines a path.

C. TCP or UDP port number: This is Layer 4 information. Standard routing decisions are made at Layer 3 using the destination IP address, not Layer 4 port numbers.

1. Cisco Systems, Inc., IP Routing: Protocol-Independent Configuration Guide, Cisco IOS XE Gibraltar 16.12.x, "Information in the IP Routing Table". This official documentation details the components of a routing table entry, explicitly listing the destination network and mask, and "the address of the next-hop router or the outgoing interface."

2. Peterson, L., & Davie, B. S. (2011). Computer Networks: A Systems Approach (5th ed.). Morgan Kaufmann. Chapter 3, "Internetworking," Section 3.2.3, "Forwarding," describes the forwarding table (or routing table) as containing entries of the form (Prefix, NextHop).

3. Almquist, P. (June 1995). RFC 1812: Requirements for IP Version 4 Routers. Internet Engineering Task Force (IETF). Section 5.2.4, "The Forwarding Table," specifies that the forwarding database must contain the destination address, next-hop router, and next-hop network interface for each route.