Pass 200-901 Exam Guide

An HTTP 404 status code indicates that the requested resource could not be found. In the context of the Cisco DNA Center API, this usually means that the URL being accessed is incorrect or the endpoint does not exist. The solution is to verify and correct the API URL to ensure it points to a valid endpoint.

Example correct API URL:

url = ' '

This ensures that the script is making requests to the correct API endpoint.

References:

Cisco DNA Center API Documentation

Cisco DevNet Associate Certification Guide

The observer pattern is designed to create a relationship where an object (subject) maintains a list of its dependents (observers) and notifies them of any state changes. This pattern achieves loose coupling between the subject and its observers, allowing them to interact without being tightly bound to each other. This flexibility ensures that changes in the subject do not heavily impact the observers, and vice versa.

The issue described indicates that HTTPS (port 443) access is not working for one specific server (172.16.50.3) in the network farm, while it works for the others. This suggests that the transport port (port 443) might be blocked or filtered for this particular server.

Transport Port Blocking: Network firewalls or security groups might block specific ports for certain IP addresses.

Server Configuration: The server might not have the necessary configuration to accept HTTPS connections on port 443.

Troubleshooting: Verifying firewall rules, security group settings, and server configurations can help identify and resolve the issue.

References:

Network Troubleshooting Guide: Troubleshooting Network Issues

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

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

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

References:

Cisco DevNet Associate Certification Guide

Cisco Ethernet Switch Operation