IPMI – technology overview

What is IPMI? This term refers to the Intelligent Platform Management Interface. It is used to connect to the server remotely. Using IPMI, you can forget about how it is to manually reboot the server: now you can fix all problems in a timely manner without leaving your home at any time. In addition, the system will help you save money on maintenance. A detailed overview of the technology, including its basic components, structure, remote access interfaces – in this article.

What is IPMI

IPMI is the best option for remotely connecting to a server and controlling its operation. Let’s consider the main features that the Intelligent Platform Management Interface has:

1. Monitoring the physical state of the equipment. For example, using IPMI, you can easily check fan speed, voltage and other indicators.
2. Restoration of service performance. You can update outdated software, reboot the system remotely, turn on the power automatically or manually.
3. Manage any peripheral devices.
4. Manage access ports and SSL certificate access protection.
5. Set up notifications about how the server is running.

But that is not all! IPMI allows you to keep a log of events, as well as store all the necessary information about the equipment that is in use. The huge advantage of the interface is that all the listed functions remain available regardless of the operation of the operating system and processor. It is enough that the server is connected to the electrical network.

IPMI 2.0 is based on a LAN network interface with its own IP address. Its use does not provide for the use of special patented devices and microcontrollers. Thus, the cost of renting a server directly depends on the cost of consumables. High-quality integrated IPMI 2.0 is, first of all:

1. Visual information about the condition of the equipment.
2. A unique set of proposals for server recovery.
3. Opportunities for collecting statistical data on all components.
4. The technology can be used with ordinary computers, not just servers.

Let’s look at 2 of the most common practical examples of IPMI:

1. The OS is installed on the rented server and you need to configure the network card. Until the network settings are made on the server, the only way to gain access to management is IPMI.

During operation, the software has frozen the remote server and it is unavailable. If you have IPMI, you can try to reboot the system with the button or turn on the server again.

Basic components of any IPMI

Considering the basic components, first of all, we will focus on the IPMI BMC. First of all, let’s answer the question, BMC what is it? Baseboard Management Controller (BMC) – IPMI controller through which the server is directly controlled. They are essentially a separate computer with its own software and a network interface located on the motherboard. The BMCs are equipped with an integrated graphics core that communicates and interacts with the main components of the motherboard.

The IPMI BMC is powered through the standby voltage of the motherboard, working always, regardless of the server. You can expand the capabilities of the basic management of the bmc interface by connecting Management Controllers, MCs. With the help of the latter, peripheral devices and voltage sources are monitored.

The controllers are connected to the BMC through the IPMB (Intelligent Platform Management Bus) interface. Through this bus, control commands are redirected to the following parts of the architecture:

1. Communication with additional controllers.
2. Reading out sensor data.
3. Access to non-volatile storage.

The main feature of the architecture is that the remote administrator is not provided with direct access to the system components. Note that you can make the controller take actions automatically. The mechanisms involved in this:

1. PEF (Platform Event Filtering) – enable, reboot the system, generate an alert.
2. Watchdog Timer – interrupts actions after a specified time has elapsed, reboots the server.
3. Firmware Firewall – Prevents potential problems by blocking IPMI commands.

Another critical component of interface IPMI is non-volatile storage. It remains available even if the CPU server has crashed and includes:

1. System Event Log (SEL);
2. Sensor Data Record (SDR) Repository;
3. Field Replaceable Units (FRUs) Info.

SEL (system event log) can be implemented with the following requirements: storing at least 16 events in memory, access to information regardless of the state of the platform and the BMC. It is possible to delete SEL. Since its memory is limited, it may be necessary to periodically clear and validate the log.

Let’s briefly talk about the main post types:

1. SDR. Data on the number and types of sensors, the ability to generate events. Stored in the Sensor Data Records Repository memory area.
2. FRU. Information about serial numbers and models of the processor, controllers, I / O boards.

Structure of IPMI Commands

IPMI is capable of transmitting messages in a request-response format, where requests are commands that initiate actions and values. Let’s consider a basic set of fields, which is the same for all commands:

1. Network Function (NetFn) – chassis, storage, event commands.
2. Request / Response Identifier – distinguishes between responses and requests.
3. Requester’s ID – informing about the source of the message.
4. Responder’s ID – an address request to a specific respondent.
5. Data – additional parameters, including the data returned in the response.

Channels for transmitting IPMI remote messages can be conditionally divided directly into BMC, System Interface (managed platform) and Serial Interface (remote administrator). Thus, the BMC acts as a switch that connects the interfaces of the system.

Remote access interfaces

The IPMI LAN Interface is used for remote access. When transmitted over a LAN, messages go through the following encapsulation stages:

1. IPMI Session Packing.
2. Encapsulation of IPMI Session via RMCP (Remote Management Control Protocol).
3. Formatting RMCP protocols in UDP datagrams.
4. Adding Ethernet frames.

Today, the serial interface for connecting the IPMI console is almost never used, but it is required to implement:

1. Serial Port Sharing (redirecting the BIOS console to the BMC module).
2. Serial-over-LAN (SoL). It is used to interact with system components that understand the serial communication interface. Also, commands are sent from the console to chips, cards and other devices.

Session and Authentication

Before you start sending ipmi messages, you need to establish a session to form an IPMI Session data packet. In essence, this is the authentication of a specific user in the IPMI network.

Now let’s look at how to connect to IPMI step by step:

1. The remote console asks for BMC data.
2. The BMC sends a response about what types of authentication are supported (for example, none, password).
3. The remote console sends a command about the selected authentication type and IPMI log.
4. Does the user have privileges to access a specific channel? The BMC’s response will contain the session ID.
5. A session activation request is sent through the remote console, containing an ID and information that identifies the user.
6. The BMC verifies the username, keys, password and sends a response about successful activation.

In some cases, sessions can be automatically terminated. This happens if during a given time interval nothing happens or the connection is broken. Is it possible to block the remote server management module? Yes, if you send a large number of requests to activate a session at the same time. The fact is that then all resources are used to track sessions that require activation.

When IPMI becomes unavailable

In some cases, the IPMI server becomes unavailable. Let’s consider the most likely causes of failures in its work in more detail:

1. Problems at the network level. These include a broken IPMI port, an insufficiently well-compressed twisted pair cable, cable defects, and equipment loss of performance.
2. Software problem. If it’s not about the IPMI port and other network elements, most likely the software is failing. The most typical options: the BMC module hangs, you need to update the firmware, module, system bug.
3. The hardware fails. We are talking about overheating, defects in the architecture of the system, breakdown of critical components.
4. Power problems. Mostly – with an IPMI server power supply.

The factors we have listed above affect both IPMI and the server. Failures of the BMC itself are quite rare, almost always the “environment” breaks down, for example, a RAM module.

IPMI in practice

IPMI management is carried out using utilities from the manufacturer, web browser, and open source utilities. Although each IPMI module has its own interface, the principle of gaining access is similar. For this you need:

1. Enter the IP-address of the BCM port into the IPMI address line.
2. Enter your password and login.

Many people are interested in how to set up Remote Control. To always have remote access to the server, you need to go to IPMI. In the remote control section, you will see a menu that allows you to:

1. reset data;
2. turn off the power immediately or gradually.

Note that the latter feature is very handy, especially if you are trying to troubleshoot remotely or disable and then re-enable the server. One of the best features is Virtual Media, which allows you to mount virtual media through a Windows share.

For dedicated servers abroad, IPMI is implemented as a KVM console, which is launched through the control panel. First, in the card with information about the server, you need to click on the console icon, which is located in the upper right corner. The console will open in your browser and adjust to the size of your screen. By the way, you can even use it via a smartphone. Remember: if you exit the panel, the session will be interrupted.

Conclusion

Summing up, we unequivocally should focus on the main advantages of IPMI:

1. Full remote access to the server and its components.
2. Registration of current events.
3. There is no dependence of the interface on the processor and OS.
4. Supports various operating systems well, as well as DOS, BIOS setup.
5. Easy to operate.
6. Securely password protected.

If you use IPMI to manage your server, you can save on system administrator services and reduce overall maintenance costs. Also, the control port allows you to control the operation of the equipment remotely, which is very convenient.

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