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 14. LAN over USB addresses
Blade
server
Logi-
cal
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
Secon-
dary
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.
Resolving conflicts with the IMM LAN over USB interface
Use any of the following actions to resolve LAN over USB conflicts with network configurations and
applications.
• For conflicts with Open MPI, configure the application so that it does not attempt to use this interface.
• Take down the interface (run iiffd
do
ow
wn
n under Linux).
© Copyright Lenovo 2017
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