Listing 2 Interfaces for the head node

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# /etc/network/interfaces on the master node
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# The loopback interface
auto lo
iface lo inet loopback

# The external ethernet interface
auto eth0
iface eth0 inet static
        address 123.45.6.789
        netmask 255.255.255.0
        network 123.45.6.0
        broadcast 123.45.6.255
        gateway 123.45.6.1

# The cluster ethernet interface
auto eth1
iface eth1 inet static
        address 192.168.0.1
        netmask 255.255.255.0
        network 192.168.0.0
        broadcast 192.168.0.255
# end of file