Cisco 200-901 - DevNet Associate (DEVASC)

When configuring a Cisco IOS XE networking device using RESTCONF, the default data encoding method is application/yang-data+json. This MIME type indicates that the data is encoded in JSON format and structured according to YANG data models. YANG (Yet Another Next Generation) is a data modeling language used to model configuration and state data manipulated by the NETCONF protocol, which RESTCONF leverages.

References:

Cisco DevNet Documentation - RESTCONF

Cisco DevNet Associate Certification Guide

In Test-Driven Development (TDD), the process starts with writing tests before writing the actual code. The primary purpose of running tests before writing the code is to ensure that the tests fail initially. This failure demonstrates that the tests are correctly identifying the absence of the desired functionality or the presence of bugs. Once the tests are verified to fail for the expected reasons, the developer then writes the minimal code necessary to pass the tests, ensuring that the new functionality works as intended and that the codebase is continuously tested.

References:

Test-Driven Development by Example

Cisco DevNet Associate Certification Guide

Device-level management allows for more granular control over the specific settings and configurations of individual network devices. This is beneficial in scenarios where fine-tuning of device settings is required, and where certain configurations may not be exposed or supported by the overarching controller. Controller-level management, on the other hand, abstracts many device-specific settings to provide a more uniform and simplified management interface, which may not support all the detailed configurations available at the device level.

References:

Cisco DevNet: Device vs. Controller Management

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

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

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

References:

RFC 1918 Address Allocation: RFC 1918

The Cisco DevNet Sandbox provides a virtual environment where engineers and developers can access and run tests on various Cisco controllers and infrastructure components. This service offers always-on and reservation-based sandboxes that simulate real-world environments.

DevNet Sandbox: The Sandbox offers various environments with preconfigured Cisco devices and APIs, allowing engineers to run tests and develop solutions without affecting live systems.

Always-On Sandboxes: These environments are always available and can be used without reservation.

API Access: The Sandbox environments include access to APIs, enabling comprehensive testing and integration.

References:

Cisco DevNet Sandbox: DevNet Sandbox

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

An ICMP "time exceeded in-transit" message indicates that the TTL (Time to Live) of a packet has expired. The TTL value is a counter that decreases by one each time the packet passes through a router. When the TTL reaches zero, the packet is discarded, and an ICMP "time exceeded" message is sent back to the sender. This typically happens when the packet takes too many hops or the destination is too far away, causing the TTL to expire before reaching the destination.

The HTTP 401 Unauthorized error indicates that the request lacks proper authentication credentials. However, in this case, the credentials are provided, so the issue likely stems from a missing or incorrect header. The Content-Type header is necessary for many REST APIs to specify the format of the request body. Adding the Content-Type: application/yang-data+json header ensures that the server correctly interprets the request as JSON formatted data according to the YANG data model.

References:

Cisco DevNet Associate Certification Guide

Cisco IOS XE RESTCONF API Documentation

For a web-based application that captures and processes credit card information, it is essential to ensure the security of the private customer data. Enabling the encryption of network traffic, typically through TLS (Transport Layer Security), protects sensitive information by encrypting data transmitted between the client and server. This prevents unauthorized access and ensures data integrity and confidentiality during the transaction process.