Immediate load shed occurs when a failure could cause the power stack to fail very quickly, for example a massive power failure where multiple power supplies go offline for any reason and the available power cannot sustain the system.

Graceful load-shedding can occur when a power supply fails and forces the power stack to re-evaluate its power allocations. Switches and powered devices may shut down in order of their default or configured priority, starting with devices with priority 27, until the power budget matches the input power. Graceful load shedding is always enabled and immediate load shedding occurs only when necessary.

What is a balanced power stack?

A balanced power stack is one that has a positive power budget; in other words, the available power is equal to or greater than the allocated power.

Balanced power budget: Available power > Allocated power

When a power stack suffers a power supply failure, the available power budget drops, and if “strict” power sharing mode has not been configured, the result is a negative power budget, causing the system to become unbalanced.

Negative power budget: Available power < Allocated power

If the allocated power is not currently being consumed, nothing would happen other than IOS messages on the console, but as soon as the allocated power is demanded by PoE devices, the system will start a load-shedding process until the power budget is balanced again.

The design of the Cisco Catalyst 3750-X switches includes hardware to assign a priority to every port in the switch. This hardware allows us to tag ports for high and low priorities, which are set by default but can be programmed by the administrator. These priorities are used only when the switch or the stack needs to shed power to bring the system back into balance. Cisco IOS Software will generate plenty of console messages to inform the administrator about the situation.

Priority Scheme

StackPower has a priority scheme that covers up to nine switches in a data stack and all of the ports in the entire stack.

Priorities are set by default when the power stack gets created but you can configure the priority of a switch or powered device to receive power (Figure 12). This priority determines the order in which devices are shut down in case of a power shortage i.e. graceful load-shedding. You can configure three priorities per system: the system (or switch) priority, the priority of the high-priority PoE ports on a switch, and the priority of the low-priority PoE ports on a switch.

Figure 12. StackPower Default Priorities

The Catalyst 3750-X has the capability to create two groups of ports, High priority and Low Priority (Figure 13). High priority ports are those connected to more important or critical powered devices and are preferred to retain inline PoE power in case of a power shortage. StackPower or the administrator assigns a priority level to those groups of ports.

© 2012 Cisco and/or its affiliates. All rights reserved. This document is Cisco Public Information.

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Cisco Systems STACKT150CM manual Priority Scheme, Balanced power budget Available power Allocated power
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STACKT150CM specifications

The Cisco Systems STACKT150CM is an advanced technology solution designed to meet the diverse networking needs of modern businesses. This system, part of Cisco's extensive product line, highlights the company's commitment to delivering reliable and high-performance networking equipment.

One of the main features of the STACKT150CM is its flexibility in deployment. The unit can be integrated into a variety of network architectures, supporting both enterprise and small business environments. Its modular design allows for efficient scalability, enabling organizations to expand their network capacity as their needs grow. This adaptability makes the device suitable for both existing networks and new setups.

In terms of performance, the STACKT150CM is equipped with high-speed switching capabilities. It operates at impressive speeds, ensuring minimal latency and reinforced reliability in data transmission. This is essential for businesses that rely on real-time data processing and communication. The device supports various protocols, enhancing its compatibility with a wide array of devices and applications within an organization’s infrastructure.

Security features are a significant focus in the design of the STACKT150CM. It incorporates advanced security measures to protect against unauthorized access and cyber threats. This includes built-in firewall capabilities and support for network segmentation, which helps isolate critical data and applications from potential vulnerabilities. With the increasing prevalence of cyberattacks, these features are essential for safeguarding sensitive information.

The STACKT150CM also leverages Cisco's innovative software-defined networking technologies, which provide enhanced control and automation capabilities. Administrators can manage the network more efficiently, allowing for quicker adjustments and responses to changing network demands. This is critical in today’s fast-paced business environment, where operational flexibility and responsiveness are paramount.

Additionally, the device boasts robust energy efficiency features. Its design minimizes power consumption without compromising performance, aligning with the growing emphasis on sustainability in technology. This not only reduces operational costs but also positions organizations as socially responsible entities.

In conclusion, the Cisco Systems STACKT150CM represents a powerful offering in network solutions, combining flexibility, security, performance, and efficiency. It is an ideal choice for businesses looking to enhance their network infrastructure while preparing for future growth and technological advancements.
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