DevNet Associate (DEVASC) v1.0 flashcards

Git rebase is a command that integrates changes from one branch onto another by moving or combining a sequence of commits to a new base commit, resulting in a linear project history.

• Rewrites commit history
• Creates a linear history (avoids merge commits)
• Moves a branch's commits to a new base
• Can be dangerous on shared branches if not handled carefully

Memory trick: Rebase makes history neat, like stacking blocks in a straight line.

Cisco SD-WAN Security Policies, configured in vManage, define a comprehensive set of security services (e.g., firewall, IPS, URL filtering, advanced malware protection) to protect traffic traversing the SD-WAN overlay network.

• Applied to vEdge routers.
• Enforces consistent security posture across the WAN.
• Configured and managed centrally from vManage.

Memory trick: vManage policies steer traffic and secure the path.

A Cisco DevNet Reserved Sandbox provides a dedicated, isolated, and customizable environment that users can book for a specific time period. It offers exclusive access to a set of Cisco devices and platforms for in-depth development and testing.

• Exclusive access for the reservation period.
• Customizable to specific topologies and software versions.
• Ideal for complex, multi-day development or testing.

Memory trick: Sandboxes offer different levels of access and control.

Wireless roaming allows a client device to maintain network connectivity as it moves between the coverage areas of different access points within the same network.

• Requires overlapping AP coverage.
• Often managed by wireless LAN controllers or intelligent APs.
• Factors like signal strength and interference influence roaming decisions.

Memory trick: Optimize Wireless: 'Coverage, Capacity, Control'

Cisco NX-OS is the operating system for Cisco Nexus switches, offering a highly programmable and modular architecture with extensive API support (REST, NETCONF/YANG) for automation and orchestration in data center environments.

• Supports various automation tools like Ansible, Puppet, Chef.
• Provides granular control over network services.
• Designed for high availability and scalability.

Memory trick: NX-OS for Nexus, Network X-tra automation.

Cisco Application Centric Infrastructure (ACI) is a software-defined networking (SDN) solution for data centers that focuses on application requirements, providing centralized automation and policy-driven application profiles across physical and virtual network infrastructure.

• Uses an APIC (Application Policy Infrastructure Controller) for centralized control.
• Employs Endpoint Groups (EPGs) for policy segmentation.
• Supports multi-vendor integration and orchestration.

Memory trick: ACI is the 'Application-Centric' brain of the data center.

SNMP is an application-layer protocol used for managing and monitoring network devices.

• Uses UDP for communication.
• Agents on devices listen for requests on port 161.
• Managers send requests and receive traps/notifications.

Memory trick: Ports are like specific doors for different network services.

NETCONF (Network Configuration Protocol) is a network management protocol that provides mechanisms to install, manipulate, and delete configuration data of network devices. YANG (Yet Another Next Generation) is a data modeling language used with NETCONF to define structured configuration and operational data.

• NETCONF uses SSH for secure transport.
• YANG defines the structure of data (schemas).
• Together, they enable programmatic, standardized device management.

Memory trick: YANG models the data, NETCONF makes the secure call.

The Webhook API in Cisco DNA Center allows external applications to receive real-time, asynchronous notifications about events occurring within the network managed by DNA Center, such as device status changes or policy violations.

• Provides event-driven communication.
• DNA Center acts as the sender, external app as the receiver.
• Eliminates the need for constant polling by the client.

Memory trick: DNA Center APIs are like a city's communication system: some for requests, some for alerts.

Encapsulation is one of the fundamental principles of Object-Oriented Programming (OOP). It refers to the bundling of data (attributes) and methods (functions) that operate on the data into a single unit (a class), and restricting direct access to some of the object's components, typically achieved through access modifiers or by simply not exposing internal details.

• Bundles data and methods into a single unit (class)
• Restricts direct access to internal state
• Hides implementation details from the outside world
• Promotes data integrity and maintainability

Memory trick: Encapsulation 'capsules' data and functions, keeping secrets safe.

The IP address of the router interface on a local network that acts as a forwarding host to other networks.

• Enables communication with devices outside the local subnet.
• Must be on the same subnet as the host.
• Often the router's IP address for that network segment.

Memory trick: Gateway Guards Global Access.

The Cisco DNA Center Network Device API provides programmatic access to discover, manage, and retrieve detailed information about network devices managed by DNA Center.

• Used for inventory management and device lifecycle.
• Endpoints for device details, interfaces, modules, and software images.
• Supports filtering and pagination for large datasets.

Memory trick: DNA Center APIs organize network control by purpose.

A Cisco proprietary advanced distance-vector routing protocol known for its fast convergence, low overhead, and scalability.

• Uses DUAL (Diffusing Update Algorithm) for fast convergence.
• Supports unequal-cost load balancing.
• Sends partial, bounded updates, reducing bandwidth usage.

Memory trick: EIGRP: Efficient, Intelligent, Great for Rapid Paths.

Webex Teams Outgoing Webhooks are configured within a Webex Teams space to send notifications (HTTP POST requests) to a specified external URL whenever a new message is posted in that space. They are crucial for chatbots to receive user input.

• Pushes messages from a space to an external endpoint.
• Includes message content, sender, and space details in the payload.
• Requires a verification token for security.

Memory trick: Webex Teams uses webhooks for flow, API for direct control.

The IOS XE RESTCONF API is an HTTP-based protocol that uses YANG data models to provide programmatic access to configure and retrieve operational data from Cisco IOS XE devices in a structured format (JSON or XML).

• Based on HTTP/HTTPS.
• Uses YANG models for data definition.
• Provides CRUD (Create, Read, Update, Delete) operations.

Memory trick: IOS XE's direct interfaces give raw power.

A connectionless Transport Layer protocol that provides minimal overhead and best-effort delivery without guaranteed reliability or ordering.

• No connection establishment (three-way handshake).
• Faster, lower latency, and less overhead than TCP.
• Suitable for real-time applications where some data loss is acceptable (e.g., streaming, gaming, DNS).

Memory trick: UDP: Unreliable, Datagrams, Pondering speed.

Fundamental security principles including Confidentiality, Integrity, and Availability, often extended with Authentication, Authorization, and Non-repudiation.

• Authentication: Verifies identity.
• Authorization: Grants permissions to access resources or functions.
• Integrity: Ensures data is accurate and has not been altered.

Memory trick: CIA+AAN: Always Authenticate, Authorize, and Never Tamper.

Cisco FSO Query APIs enable programmatic access for external applications to retrieve collected observability data, such as application performance, security events, and infrastructure metrics, based on specific query parameters.

• Used for extracting data from FSO.
• Supports various query parameters for filtering and selection.
• Essential for integration with external analysis or orchestration tools.

Memory trick: FSO's APIs are like a library: some for adding books, some for borrowing them.

Port security violation modes define the action a switch takes when an unauthorized MAC address is detected on a secure port.

• Shutdown: Disables port, sends trap.
• Restrict: Drops traffic, sends trap, increments counter.
• Protect: Drops traffic silently.

Memory trick: Port Security: 'Secure your Door, Pick your Penalty'

An Incoming Webhook in Cisco Webex Teams is a mechanism for external applications to post messages to a specific Webex Teams space using a simple HTTP POST request to a unique URL, without needing to create a full bot.

• Provides a unique URL for each webhook.
• Supports JSON payload for message content.
• Ideal for automated, one-way notifications.

Memory trick: Incoming Webhooks make messages come IN easily.

The Cisco ACI REST API is the primary northbound interface to the Application Policy Infrastructure Controller (APIC) for programmatic interaction with the ACI fabric. It allows for declarative configuration of network policies and components.

• Uses HTTP/HTTPS for communication.
• Data exchanged in XML or JSON format.
• Provides full control over ACI fabric configuration and monitoring.

Memory trick: APIC's REST API is the master key to the ACI kingdom.

The Cisco Identity Services Engine (ISE) External RESTful Services (ERS) API provides a programmatic interface for CRUD operations on ISE configuration objects, such as users, endpoints, identity groups, and network devices.

• Used for configuration management on ISE.
• Supports standard RESTful HTTP methods (GET, POST, PUT, DELETE).
• Requires specific ERS administrative privileges.
• Enables automation of ISE provisioning.

Memory trick: ISE has many doors, but ERS is for changing the guest list and rules.

A Cisco DevNet Sandbox is a free, pre-provisioned, and isolated environment that provides access to Cisco technologies (hardware and software) for developers to learn, explore, and test code and automation scripts.

• Available 24/7 or on-demand.
• Includes various Cisco platforms (e.g., DNA Center, SD-WAN, Meraki).
• Ideal for prototyping and proof-of-concept development.

Memory trick: Sandbox: safely test code before the real world.

NX-API REST is a native RESTful API on Cisco Nexus switches running NX-OS, enabling programmatic interaction for configuration and operational data retrieval using HTTP/HTTPS and supporting data formats like XML and JSON.

• Native to NX-OS.
• Uses REST principles over HTTP/HTTPS.
• Supports XML and JSON for data exchange.

Memory trick: NX-OS speaks many languages, but NX-API REST is its native structured tongue.

Cisco SD-WAN vManage is the centralized network management system (NMS) that provides a single graphical interface for configuring, monitoring, and maintaining the entire Cisco SD-WAN fabric, including policy orchestration and troubleshooting.

• Acts as the single pane of glass for SD-WAN operations.
• Used to define and apply security, routing, and application policies.
• Provides real-time and historical monitoring data.

Memory trick: vManage MANAGES everything in SD-WAN.

Cisco IOS XE Model-Driven Telemetry (MDT) is a mechanism for streaming operational data from network devices using a subscription-based, push model. It leverages YANG data models and efficient encoding (e.g., GPB, JSON) for high-frequency, structured data collection.

• Uses YANG models to define data structures.
• Push-based model (publisher-subscriber).
• More efficient and granular than SNMP polling.
• Supports various transport protocols (e.g., gRPC, TCP).

Memory trick: IOS XE offers different ways to 'listen' to its pulse.

Cisco DNA Center Network Device APIs allow programmatic access to retrieve, manage, and update information about network devices discovered and managed by DNA Center, including inventory details.

• Part of the broader Cisco DNA Center API suite.
• Used to query device details like serial number, software version, and platform.
• Enables integration with external inventory, CMDB, and asset management systems.
• Supports operations like getting device lists, device details, and device health.

Memory trick: DNA Center: APIs for every 'DNA' strand!

The TCP/IP Transport layer provides end-to-end communication between applications on different hosts, using protocols like TCP and UDP.

• Responsible for segmentation and reassembly of data.
• Uses port numbers to identify specific applications.
• TCP offers reliable, connection-oriented service; UDP offers unreliable, connectionless service.

Memory trick: Always Treat Internet Nuisances Seriously (Application, Transport, Internet, Network Access)

The Ansible `nxos_config` module is used to manage the configuration of Cisco NX-OS devices. It ensures idempotent configuration changes by comparing desired state with current state and applying only necessary modifications, often leveraging NX-API REST or NETCONF.

• Idempotent configuration management.
• Supports various configuration sections (VLANs, interfaces, etc.).
• Leverages native NX-OS APIs for structured interaction.

Memory trick: Ansible modules for NX-OS are specialized tools for tasks.

The process of routing network traffic between different VLANs using a Layer 3 switch, leveraging specialized hardware for high-speed forwarding.

• Uses Switch Virtual Interfaces (SVIs) as default gateways for VLANs.
• Performs routing in hardware (ASICs) for speed.
• More scalable and efficient than 'router-on-a-stick' for campus networks.

Memory trick: Layer 3 Switch: Lightning-fast, Luxurious, Logical routing.

Git branching is a core feature that allows developers to diverge from the main line of development and continue to work in isolation without affecting the main codebase. Each branch represents an independent line of development.

• Creates separate lines of development
• Enables parallel work on features/fixes
• Lightweight and inexpensive to create
• Can be merged back into other branches

Memory trick: Branch off to explore new code paths, then merge back to the main route.

Cisco DNA Center is an intent-based networking controller that provides centralized management, automation, and assurance for enterprise networks.

• Automates network provisioning and policy application.
• Offers a single pane of glass for network management.
• Supports both wired and wireless enterprise networks.

Memory trick: DNA is the blueprint for automated networks.

DNS is a hierarchical and decentralized naming system for computers, services, or other resources connected to the Internet or a private network.

• Translates human-readable domain names into machine-readable IP addresses.
• Primarily uses UDP port 53 for queries, TCP port 53 for zone transfers.
• Essential for web browsing and many other internet services.

Memory trick: UDP: 'Unreliable, Datagrams, Ports!'

Meraki Webhooks are automated messages sent from the Meraki cloud to a specified URL when certain events occur within the Meraki network. They enable real-time, event-driven integrations.

• Deliver push notifications to external systems.
• Triggered by specific network events (e.g., device status changes, client connections).
• Payloads are JSON formatted.

Memory trick: Meraki's APIs are like a toolbox for network interaction.

A Python set is an unordered collection of unique and immutable elements. It supports mathematical set operations like union, intersection, difference, and symmetric difference.

• Elements must be unique
• Unordered collection
• Mutable (can add/remove elements)
• Fast membership testing (O(1) average)

Memory trick: Sets ensure uniqueness, like a VIP list where everyone's distinct.

Scrum is an agile framework for developing, delivering, and sustaining complex products. It emphasizes an iterative and incremental approach, with cross-functional teams working in short cycles called Sprints.

• Iterative (Sprints)
• Incremental delivery of working software
• Roles: Product Owner, Scrum Master, Development Team
• Events: Sprint Planning, Daily Scrum, Sprint Review, Sprint Retrospective

Memory trick: Scrum sprints to deliver, collaborating every step of the way.

The Cisco SD-WAN vManage Configuration API provides programmatic access to manage all aspects of the SD-WAN network configuration, including device templates, policies, and device attachments.

• Used for declarative configuration management.
• Supports JSON payloads for data exchange.
• Enables automation of template-based deployments.

Memory trick: vManage APIs organize network control into distinct roles.

Cisco Full-Stack Observability (FSO) leverages RESTful APIs to allow programmatic access for retrieving data, managing configurations, and integrating with other tools and automation workflows.

• Enables integration with security tools and automation engines.
• Provides access to metrics, logs, and traces.
• Supports various programming languages for development.

Memory trick: FSO's RESTful API gives full observation with ease.

A webhook is an automated message sent from apps when an event occurs. It's an HTTP callback or HTTP push API, providing data to other applications in real-time.

• Real-time notification mechanism
• HTTP POST request to a specified URL
• Event-driven communication
• Reduces polling overhead

Memory trick: Webhooks push messages, ensuring everyone's in the loop instantly.

The Meraki Dashboard API is a RESTful API that provides programmatic access to the Cisco Meraki cloud management platform, enabling automation, monitoring, and configuration of Meraki networks and devices.

• Single API for all Meraki product lines.
• Administers networks, devices, and policies.
• Uses API keys for authentication.
• Accessible via the Meraki Dashboard.

Memory trick: The Meraki Dashboard API is the master key to your cloud network kingdom.

Cisco FSO Webhooks provide a mechanism for FSO to send real-time, automated notifications (HTTP POST requests) to external applications when specific events or alerts are triggered within FSO.

• Event-driven, push-based communication.
• Delivers real-time alerts and notifications.
• Integrates FSO events with external systems.
• Requires an endpoint (URL) on the receiving application to process POST requests.

Memory trick: FSO's Webhooks just Hook-up your alerts!

List comprehensions provide a concise way to create lists. It consists of brackets containing an expression followed by a `for` clause, then zero or more `for` or `if` clauses. The result is a new list resulting from evaluating the expression in the context of the `for` and `if` clauses which follow it.

• Concise syntax for list creation
• More readable than traditional loops for simple cases
• Can include conditional filtering (`if` clause)
• Can include nested loops

Memory trick: List comprehensions build new lists, filtering and transforming as they go.

Inter-VLAN routing enables communication between different VLANs, which are otherwise isolated broadcast domains.

• Requires a Layer 3 device (router or Layer 3 switch).
• Each VLAN needs a unique IP subnet and a corresponding interface on the Layer 3 device.
• Can be implemented via Router-on-a-Stick or Layer 3 switch SVI (Switched Virtual Interface).

Memory trick: Routing: 'Paths to your Destination'

Cisco DNA Center serves as the central controller for Cisco's Intent-Based Networking, enabling the definition and enforcement of consistent network policies (security, segmentation, QoS) across diverse network domains including campus, branch, and integrating with data center (ACI) and WAN (SD-WAN).

• Centralized controller for intent-based networking.
• Provides automation, assurance, security.
• Enforces consistent policy across multi-domain networks.

Memory trick: To rule many lands with one law, you need a central king, like DNA Center.

To find the network address, perform a bitwise AND operation between the IP address and the subnet mask.

• Network address is the first address in a subnet, with all host bits set to 0.
• Broadcast address is the last address in a subnet, with all host bits set to 1.
• Usable host addresses are between the network and broadcast addresses.

Memory trick: Subnetting: 'AND' to find Network, 'OR' to find Broadcast, 'Hosts' in between.

The `try-except` block in Python is used for exception handling. Code that might raise an exception is placed inside the `try` block, and code to handle specific exceptions is placed inside the `except` block.

• Handles runtime errors (exceptions)
• Prevents program crashes
• Allows for graceful error recovery
• Can catch specific exception types

Memory trick: Try to do it, if it fails, 'except' it and fix it.

Subnet mask calculation involves determining the number of host bits required to support a given number of hosts, which then defines the mask.

• Number of usable hosts = 2^h - 2 (where h is the number of host bits).
• The network and broadcast addresses are unusable for hosts.
• Smaller host bits mean a larger subnet mask (more 1s).

Memory trick: Variable Length Subnet Masks: 'Host bits Huddle, Network bits Nudge'

REST (Representational State Transfer) is an architectural style for designing networked applications. RESTful APIs use standard HTTP methods and resource-based URLs to enable stateless communication between client and server.

• Uses standard HTTP methods (GET, POST, PUT, DELETE)
• Resource-based URLs (nouns, not verbs)
• Stateless communication
• Client-server architecture

Memory trick: REST uses HTTP verbs on resource nouns, keeping communication clean.

A Denial-of-Service (DoS) attack that exploits the TCP three-way handshake by sending a flood of SYN packets without completing the handshake, exhausting server resources.

• Attacker sends SYN packets, but ignores or spoofs SYN-ACK responses.
• Server's connection table fills with half-open connections.
• Prevents legitimate clients from establishing connections.

Memory trick: SYN Flood: Server's SYNs are Never Acknowledged, leading to server collapse.

Cisco IOS XE supports RESTCONF, a RESTful HTTP-based protocol, to interact with network devices using YANG data models for configuration and operational data. This enables modern, programmatic automation and management.

• YANG models define configuration and state data structures.
• RESTCONF uses standard HTTP methods (GET, POST, PUT, DELETE).
• Provides a robust alternative to CLI for automation.

Memory trick: REST easy with YANG, it's the modern way for IOS XE.

A Python dictionary is an unordered collection of data values, used to store data values like a map, which, unlike other Data Types that hold only a single value as an element, holds key:value pair. Keys must be unique and immutable.

• Stores key-value pairs
• Keys must be unique and immutable
• Values can be of any data type
• Highly efficient for key-based lookups (average O(1) time complexity)

Memory trick: Dictionaries are like fast indexes, finding keys instantly.

The CIA Triad (Confidentiality, Integrity, Availability) is a fundamental model for information security policies.

• Confidentiality: Protecting information from unauthorized access.
• Integrity: Ensuring information is accurate and has not been tampered with.
• Availability: Guaranteeing authorized users can access information when needed.

Memory trick: CIA: 'Confidentiality, Integrity, Availability' is the security core.

The number of usable host IP addresses in a subnet is calculated by taking 2 to the power of the number of host bits, minus 2 (for the network and broadcast addresses).

• Host bits are 32 minus the CIDR prefix length.
• Network address is the first address in the subnet.
• Broadcast address is the last address in the subnet.

Memory trick: Hosts Count: 'Two to the Power of Host Bits, Minus Two'

TCP and UDP are the two primary Transport layer protocols, differing in reliability, connection establishment, and overhead.

• TCP: Connection-oriented, reliable, ordered delivery, error checking, flow control.
• UDP: Connectionless, unreliable, best-effort delivery, low overhead, faster.
• Applications choose based on their reliability and speed requirements.

Memory trick: Reliability: 'TCP Cares, UDP Dares'

A VPN extends a private network across a public network, enabling users to send and receive data across shared or public networks as if their computing devices were directly connected to the private network.

• Creates an encrypted tunnel for data transmission.
• Provides confidentiality, integrity, and authentication.
• Commonly used for remote access and site-to-site connectivity.

Memory trick: Secure your Network: 'Protect, Encrypt, Authenticate'

NETCONF is a network management protocol that provides mechanisms to install, manipulate, and delete device configurations. YANG is a data modeling language used to define the structure and constraints of configuration and state data.

• Uses XML encoding for data exchange.
• Provides transactional configuration capabilities.
• YANG models define hierarchical data structures.

Memory trick: YANG models give NETCONF the blueprint for the network.

RESTCONF is a REST-like protocol that provides programmatic access to network devices using data models (YANG) for both configuration and operational data, leveraging standard HTTP methods.

• Uses HTTP methods (GET, POST, PUT, DELETE) over HTTPS.
• Relies on YANG data models for structured data.
• Supports both configuration and operational data retrieval.
• More modern and structured than CLI scraping or SNMP for certain tasks.

Memory trick: IOS XE: Your Network's RESTful API!

The Webex Teams REST API provides a programmatic interface to interact with Webex Teams, allowing developers to send messages, manage spaces, add members, and perform other actions using standard HTTP methods.

• Uses standard RESTful principles (HTTP methods, JSON payload).
• Enables comprehensive control over Webex Teams functionalities.
• Requires authentication (e.g., OAuth token).

Memory trick: To build a Webex Teams robot, you need the REST API as its brain.

The process of determining the appropriate subnet mask to create subnets of a specific size, minimizing IP address waste.

• Number of usable hosts = 2^n - 2, where n is the number of host bits.
• A smaller 'n' (fewer host bits) means a larger subnet mask and fewer hosts.
• A /27 mask provides 30 usable hosts (2^5 - 2).

Memory trick: Host Bits: How Many To Serve?

The Requests library is a popular, elegant, and simple HTTP library for Python, designed to simplify making HTTP requests. It handles many complexities automatically, such as connection pooling, SSL verification, and JSON encoding/decoding.

• Simplifies HTTP requests (GET, POST, PUT, DELETE)
• Automatic JSON serialization/deserialization
• Handles headers, parameters, authentication
• Not built-in, needs installation (`pip install requests`)

Memory trick: Requests 'asks' and 'receives' JSON with ease, like a polite server.