2. IPU-Machine BMC specification

The IPU-Machine baseboard management controller (BMC) runs software based on the OpenBMC project.

The responsibilities of the BMC software stack are to control, monitor and manage system hardware, including power, sensors, inventories and event logging.

You can control and monitor the system, via the BMC, using a variety of user interfaces such as a command line interface (CLI), REST API, IPMI and Redfish.

2.1. BMC subsystem

A block diagram of the IPU-Machine, showing the BMC subsystem, is shown in Fig. 2.2.

The physical components in the BMC subsystem are:

  • ASPEED AST2520 baseboard management controller

  • System FPGA

  • 128 MB serial boot flash

  • 1 GB of DDR4 DRAM

  • One USB port: Micro-USB management interface, see Fig. 13.1

  • 1 GbE management Ethernet interface, eth0, which is configured to 100 Mbps, full-duplex with auto-negotiation enabled on BMC boot

  • 1 GbE internal Ethernet interface, eth1, which is configured to 100 Mbps, full-duplex with auto-negotiation enabled for communication between BMC and IPU-Gateway

  • Two I2C PSU interfaces for monitoring the state of the power supplies

  • Five fan interfaces for controlling and measuring the speed of the system cooling fans

  • Three LEDs used to indicate status

2.1.1. System FPGA

The FPGA is mainly a status and control signal concentrator. It ensures that those control signals are always in a safe state. In addition, it provides hardware monitoring and protection for any thermal or voltage abnormalities. It also controls the sequencing of supply voltages, clocks and reset signals.

2.1.2. LEDs

There are three LEDs used to indicate status:

  • Green indicates normal operation status

  • White is used to “locate” or identify a specific IPU-Machine in a system

  • Yellow indicates various error conditions:

    • Temperature alert detected

    • Standby voltages detected failing

    • PSUs detected failing

    • Connector domain detected failing

    • IPU-Gateway 1 domain detected failing

    • IPU 1 and 2, or IPU 3 and 4 domains detected failing

    • Fan fail detected (too few fans or fans running too slow)

    • No profile configuration found in flash

    • BMC flash not trusted


The white locator LED can be turned on and off with either the CLI or over IPMI.

Using the CLI:

$ ipum-utils locator_led_on
$ ipum-utils locator_led_off

Using IPMI:

$ ipmitool -I lanplus -C 3 -p 623 -U <bmcuser> -P <bmcpass> -H <bmcip> chassis identify <interval>

where <interval> is the time in seconds (default 15 and max 255) that the white locator LED remains lit.

2.1.3. Ethernet switch

There is an Ethernet switch on the IPU-M2000 motherboard that is set up by BMC and can be configured over the BMC CLI or REST interface, to provide different connectivity options between IPU-M2000 components and external network.

Below are description of notable ports of this Ethernet switch with a picture to help visualizing it.

  • Port 1 : Connected to upper RJ45 connector on IPU-M2000 front panel

  • Port 2 : Connected to lower RJ45 connector on IPU-M2000 front panel

  • Port 5 : Connected to BMC Ethernet interface

  • Port 6 : Connected to IPU-Gateway Ethernet interface


Fig. 2.1 IPU-M2000 simplified Ethernet switch connectivity

This Ethernet switch can be configured in three different forwarding modes with respect to these ports:

  • BmcOnly: BMC can send and receive traffic to and from port 1 and port 2. IPU-Gateway traffic is blocked.

  • BmcGatewaySplit: BMC can only send and receive traffic to and from port 2. The IPU-Gateway can only send and receive to and from port 1.

  • Open (default): BMC and IPU-Gateway can send and receive traffic to and from port 1 or port 2.

You can configure the Ethernet switch to one of the above modes using the BMC CLI as below:

$ ethswitch-fix -s BmcOnly
$ ethswitch-fix -s BmcGatewaySplit
$ ethswitch-fix -s Open

You can configure the Ethernet switch to one of the above modes using BMC over REST as below:

$ curl -k -X PUT https://<bmcip>/xyz/openbmc_project/ethswitch/mode/attr/Mode -d '{"data":"xyz.openbmc_project.ethswitch.Mode.State.BmcOnly"}' -u <bmcuser>:<bmcpass>
$ curl -k -X PUT https://<bmcip>/xyz/openbmc_project/ethswitch/mode/attr/Mode -d '{"data":"xyz.openbmc_project.ethswitch.Mode.State.BmcGatewaySplit"}' -u <bmcuser>:<bmcpass>
$ curl -k -X PUT https://<bmcip>/xyz/openbmc_project/ethswitch/mode/attr/Mode -d '{"data":"xyz.openbmc_project.ethswitch.Mode.State.Open"}' -u <bmcuser>:<bmcpass>

2.2. BMC functions

The BMC supports the following system management functions:

2.3. IPU-Machine block diagram


Fig. 2.2 IPU-M2000 BMC block diagram

2.4. Supported IPMI commands

This section summarises the ipmitool commands supported by the BMC. For details of the parameters and examples of use, see the appropriate user guide chapter.

The BMC is tested with ipmitool version 1.8.18.

Table 2.1 Inventory monitoring



fru print

Display information about all FRUs

fru print <fruid>

Display information about the FRU with the specified ID

Table 2.2 Events and logging



sel clear

Clear all event logs

sel list

Display list of events

sel elist

Display list of events with extended information

Table 2.3 Network configuration



lan print

Print network information

ipsrc dhcp

Enable DHCP

ipsrc static

Configure static IP

ipaddr <ip_address>

Set IP address

netmask <x.x.x.x>

Set IP address

defgw ipaddr <ip_address>

Set default network gateway IP address

Table 2.4 Power operations



power off

Hard power off

power soft

Soft power off

power reset

Warm reboot

power on

Power on

bmc reset cold

BMC reboot

dcmi power get_limit

Get current status of power cap

dcmi power set_limit limit <limit>

Set new power cap value

dcmi power activate

Enable power capping

dcmi power deactivate

Disable power capping

Table 2.5 Sensor monitoring



sdr list

Display SDR entry readings and their status

sdr elist

Display extended sensor information

sensor thresh <sensor_name> lcr <value>

Set sensor lower critical threshold

sensor thresh <sensor_name> lnc <value>

Set sensor lower non critical threshold

sensor thresh <sensor_name> unc <value>

Set sensor upper non critical threshold

sensor thresh <sensor_name> ucr <value>

Set sensor upper critical threshold

sensor list

Display sensors and thresholds in a table format

sdr get <sensor_name>

Display sensor information

sdr type

Display a list of sensor types

sdr type <sensor_type>

Display SDR repository records of a sensor type


Sensor thresholds values in sensor thresh command should match this equation: lcr <= lnc <= unc <= ucr

Table 2.6 Serial over LAN (SoL)



sol activate

Access serial over LAN (SoL) interface

Table 2.7 Time settings



sel time set “DD/MM/YYYY HH:MM:SS”

Set time and date (will fail if system is in NTP mode)

sel time get

Get time and date

Table 2.8 User management



user summary [<channel_number>]

Print a summary, including number of users on the system

user list [<channel_number>]

List users

user set name <user_id> <username>

Create a user with <user_id> and <username>

user set password <user_id> [<password> <16|20>]

Create a password for user with <user_id> (the password can be 16 or 20 bytes in length)

user enable <user_id>

Enable user with <user_id> (must be done after creating user and password)

user disable <user_id>

Disable user with <user_id>

user priv <user_id> <privilege_level> [<channel_number>]

Set privilege level for user with <user_id>

channel setaccess <channel> <user_id> ipmi=on

Enable IPMI access for a user

  • The maximum number of system users is 30

  • The maximum number of users with IPMI access is 15

  • The maximum username length for an IPMI user is 16 bytes

  • User IDs are from 1 to 15

  • Passwords must be a minimum of 8 characters in length

  • The privilege levels are:

    • 0x1: Callback

    • 0x2: User

    • 0x3: Operator

    • 0x4: Administrator

    • 0x5: OEM Proprietary

    • 0xF: No Access