[Beowulf] Fundamental HPC cluster problem

John Thingstad jpthing at online.no
Mon Jul 20 06:47:27 PDT 2015

I am having problems with my simple cluster. It is a Powerede server and 
10 Pi 2's.

I can't set up DHCP and NAT.
My network configuration is one server having two server ports one to 
the local router and one to the cluster.


This my journal :

  This will be a RasPi cluster.

 From ADA Fruit I got:

  * 10 x Raspberry Pi 2 - Model B - ARMv7 with 1 GiB RAM
  * 10 x Rapberry Pi B+/ 3 Frosted white enclure
  * 10 x USB Cable with Switch -A /MicroB
  * 10 x SD/MicroSD Memory Card (8 GiB SDHC

 From Komplett I got:

  * TP-LINK Gibabit unmanaged switch, 24 port TL-SG1024G
  * 10 port USB HUB with power adapter
  * 1 Gib single port Ethernet Card


  * 100 m Cat5e Cable
  * Cable plier tool
  * Cable tester

I already have a Dell PowerEdge  T110 II server

It has:

  * Intel i3.2120 CPU @ 3.3 GHx
  * DIMM DDR3 Synchronous 1600 MHz 8 GiB
  * Seagate ST500NM0011 500 GiB
  * 3 x 1 Gib Ethenet Ports

I Atso have a Jensen AL59300 V3 router
             5 x 1GiB Ethernet ports, Wireless acgh

Rough description of the hardware installing:

Procedure for server:

 1. Added Ethernet card to Server. Now eth0 if connected to home router.
    Installed Ethernet card so eth3 is available for  switch.
 2. Made 1 x 5 m cable for connection from switch to server

Procedure for each of the 10 x Pi's:

 1. Made a approx 30 cm cables for the Pi
 2. Put Pi in eclosure.
 3. Install NOOBS on MicroSD.
 4. Form that install RasPI
 5. Connect USB cable from MicroUSB port on Pi to USB port on USB HUB.
 6. Connect Ethernet cable from Pi to Switch

A carboard box was cut and used to fit the pi's the USB hub and the 
switch in such a way to have easy access to the switches on the USB 
cables from the PI's to the USB HUB.

Setting up NAT and DHCP:

In /etc/network/interfaces add

auto eth3

iface eth3 inet static



in /etc/sysctl.conf

uncomment net.ipv4_forward=1

in /etc/default/isc-dchp-server

set INTERFACES="eth3"

For NAT:

In /etc/rc.local add

/sbin/iptables -P FORWARD ACCEPT

/sbin/iptables --table nat -A POSTROUTING -o eth0 -j MASQUERADE


sudo apt-get install isc-dhcp-server

setup /etc/shcp/dhcpd.conf to:

default-lease-time 600;

max-lease-time 7200;

option subnet-mask;

option broadcast-address;

option routers;

subnet netmask {




arp -a
eth0 only

What is wrong?
I suspect the NAT , but I am not sore how to proceed or diagnose this 
Can someone help?

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