What is IPMI?
IPMI (Intelligent Platform Management Interface) is a set of specifications that lets administrators monitor and control a server's hardware through its baseboard management controller (BMC), without relying on the host operating system. Intel, Dell, HP and NEC published the first version in 1998, and many other hardware vendors later adopted it. Because the BMC has its own processor, firmware and network connection, IPMI keeps working when the OS has crashed, the boot disk has failed or the server is powered off, as long as the BMC still receives standby power. That makes it a basic building block of out-of-band management.
How IPMI works
The BMC sits at the center. It reads sensors on the motherboard, stores events and answers commands that arrive over a local system interface or over the network. Remote commands travel inside RMCP or RMCP+ packets on UDP port 623. The main building blocks are:
- BMC: the microcontroller that runs the IPMI firmware and manages the platform.
- Sensor Data Record (SDR) repository: describes each sensor, its units and its thresholds.
- System Event Log (SEL): a nonvolatile log of hardware events such as memory errors or fan failures.
- FRU inventory: part and serial numbers for boards, power supplies and other field-replaceable units.
- Serial over LAN (SOL): redirects the server's serial console over the network.
A worked example with ipmitool
Most engineers meet IPMI through the open source ipmitool utility. Take a server whose BMC sits at 10.20.0.15 on a management VLAN. Running ipmitool -I lanplus -H 10.20.0.15 -U opsadmin -E sensor list returns each sensor with its current value and thresholds, for example CPU1 Temp at 68 °C against an upper critical threshold of 95 °C. The command chassis power status shows whether the host is on, chassis power cycle restarts a hung machine, and sel list prints events such as a power supply losing AC input. The -E option reads the password from an environment variable, which keeps it out of shell history.
Add sel list to your regular inspection routine so hardware events are reviewed and the log is cleared before it fills.
IPMI vs Redfish
Redfish, published by the DMTF in 2015, is the newer standard for the same job. IPMI uses compact binary messages over UDP. Redfish uses a REST API with JSON over HTTPS, so standard web tooling and scripting languages can call it directly. Redfish also describes modern hardware such as storage controllers, GPUs and firmware inventory in more detail. Many current servers support both, and IPMI remains common in older fleets and in scripts written around ipmitool. A practical plan is to keep IPMI for legacy systems and move new automation to Redfish where the BMC firmware supports it.
IPMI security risks
IPMI was designed for trusted management networks, and its weaknesses are well documented. IPMI 1.5 offers only weak authentication on the network. IPMI 2.0 added RMCP+ with stronger authentication and encryption, but its RAKP handshake lets an unauthenticated requester retrieve a salted password hash that can be cracked offline (CVE-2013-4786). Some BMCs have also shipped with cipher suite 0 enabled, which accepts commands without a valid password. Practical controls:
- Disable IPMI over LAN on servers you manage through Redfish or the vendor web interface.
- Disable cipher suite 0 and IPMI 1.5 access.
- Place BMCs on an isolated management VLAN with source address filtering.
- Replace vendor default credentials with unique, long passwords.
- Keep BMC firmware up to date.
How CloudSino approaches IPMI
CloudSino DCOS is an out-of-band hardware monitoring and control platform that connects to server BMCs through IPMI 2.0, Redfish and vendor interfaces such as iDRAC, iLO, iBMC and XCC. Through the out-of-band channel it collects sensor data such as temperature, fan speed and voltage, raises alerts on hardware sensor anomalies, and supports remote power on, power off, restart and KVM over IP console access. DCOS records out-of-band operations for audit, and it can detect IPMI configuration security issues and feed them into its alerting.
Frequently asked questions
Which port does IPMI use?
Remote IPMI, often called IPMI over LAN, uses UDP port 623 for RMCP and RMCP+ traffic, and Serial over LAN runs inside the same RMCP+ session. The BMC web interface and graphical console are vendor features that use other ports, usually HTTPS on 443 plus vendor-specific ports for video redirection.
Does IPMI work when the server is powered off?
Yes, as long as the server is plugged in and the BMC has standby power. The BMC can then report sensor and inventory data and power the host on. If the power supplies lose their input, the BMC goes offline together with the server.
Is IPMI the same as iDRAC, iLO or XCC?
No. iDRAC (Dell), iLO (HPE) and XCC (Lenovo) are vendor BMC products. Each implements IPMI and Redfish alongside its own web interface, license tiers and extra features such as virtual media. IPMI is one of the common protocols those controllers share.
What is the difference between in-band and out-of-band IPMI?
In-band, a tool running on the host OS talks to the BMC through a local driver and system interface such as KCS. Out-of-band, the tool connects over the network to the BMC's LAN channel. Only the out-of-band path still works when the operating system is down.