300-915 Sample Questions & Answers

MQTT is designed for low-power, constrained devices and unreliable networks, making it ideal for this scenario. QoS level 1 (At Least Once) ensures that the message is guaranteed to be delivered by requiring an acknowledgment (PUBACK) from the broker. If the client doesn't receive the acknowledgment, it will resend the message, which handles the intermittent connectivity issue. QoS 2 is overkill and adds more overhead, while QoS 0 provides no delivery guarantee.

A gauge is specifically designed to display a single metric's current value in relation to a set range. By setting color-coded thresholds for safe (green), warning (yellow), and critical (red) ranges, the operations team can immediately assess the temperature status of a machine at a glance. A line graph is better for trends over time, a pie chart for proportions, and a bar chart for comparing discrete values.

LoRaWAN (Long Range Wide Area Network) is a communication protocol specifically designed for low-power, long-range communication between IoT devices (sensors) and a central gateway. The LoRaWAN Gateway is the component that receives the wireless signals from the sensors and forwards the data to the rest of the network via a standard connection like Ethernet, which is then handled by the switch and router.

For applications like real-time video analytics, latency is a critical factor. Processing video feeds at the edge eliminates the delay of sending large amounts of data to a centralized cloud, waiting for processing, and receiving a response. This allows for immediate actions and decisions, such as stopping a machine in case of a safety violation. While other factors like data storage and bandwidth costs are benefits of edge computing, minimizing latency is the primary driver for this type of application.

The resources section of the package.yaml file is where an application's requirements are defined. This includes not only CPU and memory but also devices (like serial ports) and volumes for persistent storage. The network section defines networking aspects, health-check defines monitoring, and app-config is for application-specific environment variables.

Cisco Identity Services Engine (ISE) provides extensive profiling capabilities. It can use probes like DHCP, DNS, and NetFlow, as well as deep packet inspection of industrial protocols (e.g., CIP, PROFINET), to identify and classify endpoints that cannot actively authenticate via 802.1X. Once a device is profiled, ISE can apply dynamic access policies, such as assigning it to a specific VLAN or applying a downloadable ACL, effectively segmenting the network.

The IoT Hub Hostname (e.g., my-iot-hub.azure-devices.net) is the unique endpoint for the specific IoT Hub instance that the data will be sent to.

The Shared Access Key is the secret key used to generate the Shared Access Signature (SAS) token. The SAS token is then used to authenticate the connection to the Azure IoT Hub.

The show mac address-table command on a Cisco switch displays the MAC address forwarding table. This table lists all the MAC addresses the switch has learned, the VLAN they belong to, and the physical port on which they were learned. This is the correct command to verify Layer 2 connectivity and find the MAC address of a directly connected device like a PLC.

The best practice is to use a private, trusted container registry. Before images are pushed to this registry (or pulled for use in a build), they should be scanned for known vulnerabilities (CVEs). This ensures that the base layers of the application are secure. Tools like Clair, Trivy, or commercial solutions integrated into registries can perform this scanning as part of the CI/CD pipeline, failing the build if high-severity vulnerabilities are found.

The root cause of the problem is the application's memory consumption exceeding its allocation, causing the IOx supervisor to terminate it. The most direct and effective solution is to address the source of the high memory usage within the application code itself. This involves profiling the code, identifying memory leaks or inefficient data structures, and optimizing them. Simply increasing the memory allocation might be a temporary fix but does not solve the underlying problem and may not be feasible on resource-constrained edge devices.