Chapter 6. Accessing the IMM
Unlike a baseboard management controller, the IMM does not require IPMI device
drivers or USB daemons for in-band IMM communication. Instead, a LAN over
USB interface enables in-band communications to the IMM; the IMM hardware on
the system board presents an internal Ethernet interface from the IMM to the
operating system. LAN over USB is also called the USB in-band interface in the
IMM Web interface.
In a scalable blade complex, each IMM is shown as a LAN over USB device in the
operating system. For each blade server in the scalable blade complex to be a
unique and known IP address, both blade servers have different default IP
addresses. The default IP address for the primary blade server is 169.254.95.118,
and the Keyboard Controller Style (KCS) address is 0x6CA8.
For packets to be routed correctly from the host to the IMMs, each of the LAN
over USB interfaces must appear on a separate subnet to the host. The IMM
implements a DHCP server that services only the LAN over USB interface. It
assigns the subnet mask on the LAN over USB interfaces for the host to
255.255.255.0.
The following table shows the IP addresses for each of the blade servers in a
complex.
Table 13. LAN over USB addresses
Blade
server
Logical
node
ID
IMM IP
address Host address Host subnet Host subnet mask
Keyboard Controller
Style (KCS) address
Primary 0 169.265.95.118 169.254.95.120 169.254.95.0/24 255.255.255.0 0x8CA6
Secondary 1 169.265.96.118 169.254.96.120 169.254.96.0/24 255.255.255.0 0x8CA8
LAN over USB devices are not aware of LAN over USB devices in other partitions.
If you configure the two blade servers as two independent partitions in a scalable
blade complex, each blade server is considered to the primary blade server of the
hardware partition that contains that blade server. The logical ID of the primary in
each partition is 0 and the default IP address of each primary blade server is
169.254.95.118.
Potential conflicts with the LAN over USB interface
In some situations, the IMM LAN over USB interface can conflict with certain
network configurations, applications, or both.
For example, Open MPI (Message Passing Interface) attempts to use all the
available network interfaces on a server. Open MPI detects the IMM LAN over
USB interface and attempts to use it to communicate with other systems in a
clustered environment. The LAN over USB interface is an internal interface, so this
interface does not work for external communication with other systems in the
cluster.
© Copyright IBM Corp. 2011 107
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