HP XC System Software Hardware Preparation Guide Version 3.1

The head node in an HP XC system is always the node connected to the highest port number of any node
on the Root Administration Switch and the Root Console Switch.
NOTE: The head node port is not the highest port number on the Root Administration Switch. Other
higher port numbers are used to connect to other switches. If the Root Administration Switch is a ProCurve
2848 switch, the head node is connected to port number 42, as discussed in “Root Administration Switch”
(page 23).
If the Root Administration Switch is a ProCurve 2824 switch, the head node is connected to port number
22 on that switch, as discussed in “Root Administration Switch” (page 23). The head node should, however,
be connected to the highest port number on the interconnect switch.
The next node connected directly to the root switches (Administration and Console) should have connections
to the Quadrics switch at the next highest port number on the Quadrics switch (max-node minus 2). All
nodes connected to the Root Administration Switch will be connected to the next port in descending order.
Nodes attached to branch switches must be connected starting at the opposite end of the Quadrics switch.
The node attached to the first port of the first Branch Administration Switch should be attached to the first
port on the Quadrics switch (Port 0).
2.4.2 Gigabit Ethernet Interconnect Connections
The HP XC System Software is not concerned with the topology of the Gigabit Ethernet interconnect, but
it makes sense to structure it in parallel with the Administration Network in order to make your connections
easy to maintain.
Because the first logical Gigabit Ethernet port on each node is always used for connectivity to the
Administration Network, there must be a second Gigabit Ethernet port on each node if you are using
Gigabit Ethernet as the interconnect.
Depending upon the hardware model, the port can be built-in or can be an installed card. Any node with
an external interface must also have a third Ethernet connection of any kind to communicate with external
networks.
2.4.3 Administration Network Interconnect Connections
In cases where an additional Gigabit Ethernet port or switch may not be available, the HP XC System
Software allows the interconnect to be configured on the Administration Network. When the interconnect
is configured on the Administration Network, only a single LAN is used.
However, be aware that configuring the system in this way may negatively impact system performance.
To configure the interconnect on the Administration Network, you include the --ic=AdminNet option
on the discover command line, which is documented in the HP XC System Software Installation Guide.
If you do not specify the --ic=AdminNet option, the discover command attempts to locate the highest
speed interconnect on the system with the default being a Gigabit Ethernet network that is separate from
the Administration Network.
2.4.4 Myrinet and InfiniBand Interconnect Connections
The other interconnect types that are supported (such as Myrinet and InfiniBand) do not have the ordering
requirements of the Quadrics interconnect, but it makes sense to structure it in parallel with the other two
networks in order to make your connections easy to maintain and service.
The port numbering on these other interconnect switches starts at number 1 in contrast to the port
numbering on the Quadrics interconnect switch, which starts at number 0.
2.4 Interconnect Connections 29